Saying the galaxy is in constant conflict between Force users is wrong. It is true that most Star Wars media focuses on periods of conflict because those are the periods which are exciting and make good stories. But you have to remember that the Old Republic was 25,000 years old by the time the Sith finally managed to actually destroy it.
That's more than
five times longer than the entirety of the time since humans invented writing to today (admittedly the Republic went through a lot of changes in that time, but there was no period where there wasn't a government which called itself the Galactic Republic which dominated the Core worlds).
Yes, there were periods when various Force users caused conflict, and those conflicts could last centuries or even over a thousand years, but for at least eighty percent of the Republic's history,
there were no major Force-user conflicts. Oh, sure there were probably minor heresies and small scale (limited to maybe a dozen planets or so at a time) conflicts, but the Force-users were not the ones in the driver's seat.
Let's see, here's the timeline of major Force related conflicts (as sourced from Wookipedia)[Note: I'm exculding the Ratakan Infinte Empire because that was more or less an actual empire who's rulers were Force users, and not a conflict
between Force users)
~25,700 BBY (Before Battle of Yavin/A New Hope) Years pre Republic the
Force Wars split the Je'daii Order (the original Jedi from Tython, brought there by mysterious ships 10,000 years before, and then formed a philosophy where balance between Light and Dark sides in an individual was enforced on pain of exile) following a Ratakan invasion. By the time the dust settled, Tython was barely habitable, but the Je'daii Order had rejected the idea that balance between the Light and Dark sides was a good thing and reformed into the Jedi Order exclusively using the Light side, while the Bogan (Dark Side) fled the Jedi then hunted down the Bogan users. This conflict lasted about 10 years, even though it took about seven centuries for the fallout to settle.
~25,000 BBY A
series of wars between various planets in the Core leads to the formation of the Old Republic with the help of the Jedi Order (based on their new homeworld of Ossus), who assume an unofficial role as peacekeepers.
~24,500 BBY
First Great Schism, conflict between the centralized Jedi council on Ossus and a splinter groups who simultaneously wanted less oversight, and more active intervention in the galaxy (potentially by military force, and subverted by the Dark side), this was a short conflict, no longer than a few years.
~24,000-7,000 BBY No major Force User conflicts. Although there's nearly a dozen Republic civil wars (mostly between Coruscant and Alaskan over which should be more powerful), wars with the Hutts, several wars of expanion, ect. There's even a thousand year period* where the galaxy is in a state of constant total war which had nothing to do with Force users (although a lot to do with xenocide and xenophobia).
*~12,000-11,000 BBY The Republic is taken over by a human-centric religious cult which launches over twenty-three different crusaders to conquer non-human worlds. This ends when the Jedi (who had withdrawn from the Republic following the cult's ascension) with the help of the Bureau of Ships and Services assume direct control of the Old Republic after nearly 1,000 years of human-centric theocratic rule which had resulted in a state of constant war.
~7,000-6,900 BBY
Second Great Schism leads to the
Hundred Years of Darkness, when a bunch of Jedi alchemists to the Dark Side and start a war with the Jedi. Fighting lasts a century, and created a number of horrors, such as Ranchors and Rackghols thought Dark side alchemy. The alchemists lose and the Jedi, in the hopes that they will reform, exile them. The exiles land on the Korriban, the Sith homeworld, which they then took over, and thus adopted the name Sith for themselves and Ajunta Pall becomes the first Dark Lord of the Sith. (It should be noted, that this conflict, while bad and created monstrosities, was mostly limited to Jedi controlled worlds and the rest of the galaxy was mostly unaffected)
~5,000 BBY In an attempt to prevent a Sith civil war (and incidentally unify the Sith behind himself) Dark Lord of the Sith Naga Sadow starts the
Great Hyperspace War against the newly contacted Galactic Republic (which it must be noted was many, many times the size of the Sith Empire, and had a lot better maps and navigation technology). This was undeniably a
bad idea. War engulfs the galaxy as the highly militarized Sith Empire takes the relatively decentralized and somewhat peaceful Republic by complete surprise. Billions die, the Sith get all the way to Coruscant before the Republic mobilizes and the Jedi neutralize Naga Sadow's Battle Meditation, but the Republic is still many, many times the size of the Sith Empire and once fully mobilized steamrolls the Sith in less than a year. The Chancellor of the Republic (a non-Force user) then orders a total purge of Sith space, nearly wiping out the Sith species and rendering Korriban lifeless. The splintered remains of the Sith go into hiding. (This is also the point where the Star Cabal was formed)
~4,600 BBY A brief conflict in the reconsituted Sith Empire (still in hiding) happens when Sith Lord
Kel'eth Ur falls to the Light side.
~4,250 BBY The
Third Great Schism happens when a number of Jedi who were studying the Sith teachings fall to the Dark side. Major fighting occurs on Coruscant, before the Dark Jedi retreat to the Vultar System, which they accidentally destroy.
3998-3995 BBY Exar Kun and Ulic Qel-Droma fall to the Dark side and use the teachings of the Sith (and the tutalage of several Sith Force Ghosts) to form the Brotherhood of the Sith (who are totally separate from the reconstituted Sith Empire, which is still in hiding), this leads to galaxy wide battles as the Sith Brotherhood attempt to conquer the Republic in the
Great Sith War. The Jedi homeworld of Ossus is devestated and the Jedi relocate their headquarters to Coruscant.
~3978-3960 BBY The Sith Empire manipulates the
Mandalorians into war with the Republic to test their defenses. The Republic does badly until Revan leads a contingent of Jedi against the Jedi Council's orders against the Mandalorians. This was a
bad idea. The Sith wanted to test the Jedi more than the Republic, and by entering the war Revan gave them exactly what they wanted. The pressures of war, combined with the knowledge that the someone was manipulating the Mandalorians leads Revan to lead his group of Jedi into the unkown, where they are captured and turned by the Sith.
~3959-3950 BBY The turned Revan starts the Jedi Civil War, which spawns a whole series of internecisne conflicts where Revan's Sith and the Jedi clash with the Republic caught in the middle. This brings an end to the Old Sith Wars, which had started with the fall of Exar Kun nearly 50 years before.
3681-3653 BBY After nearly 2,300 years in hiding the Sith Empire attacks the Republic starting the
Great Galactic War. This war lasts nearly 30 years of total war, and ends with an unexpected peace treaty which sets up the Republic and Sith Empire as rough equals in a proxy war.
3653-3642 BBY The Treaty of Coruscant sets the stage for the
Galactic Cold War which lasts about a decade before the Sith Empire and Republic go to war again.
3642-3636 BBY The
Galactic War rages, the Sith Empire makes impressive inroads towards the Core, before infighting and hardened Republic resistance breaks the Sith offensive. The Sith then go from defeat to defeat as their Emperor goes totally silent and is nearly on the verge of defeat before a
third side lead by the Sith Emperor intervenes in the conflict and conquers both sides. (Yes, both the Republic/Jedi and the Sith are conquered, by the Sith's own emperor; and you thought Palpatine's plans could be convoluted)
3632-3630 BBY
The Jedi and Sith work together to overthrow the Eternal Empire.
3630-36?? BBY The
Third Galactic War between the Republic/Jedi and the Sith Empire. Eventually the Republic wins and the Sith Empire and Sith Order are destroyed.
~2000 BBY The
Fourth Great Schism occurs, a Jedi Master falls to the Dark side, unifies the tribal remnants of the Sith Empire and starts the
New Sith Wars. This was a Bad Idea.
~2000 BBY-1000 BBY The
Republic Dark Ages, the Sith fracture and come back again and again over a 1,000 year period where conflicts splinter the galaxy as groups which had been kept in check by the Jedi take advantage of their distraction to settle old grudes. Massive amounts of technology are lost and trillions die in seemingly never ending wars.
1000 BBY The conflicts finally
end when Darth Bane arranges the death of every other Sith along with the Jedi Lords (as the Jedi had increasingly become powers unto themselves in those dark times). The temple Jedi of the Coruscant temple (who had mostly remained on Coruscant during the conflicts, and thus were not present at the Battle of Rushan) assume total control over the Jedi Order and the Republic starts a series of reforms which lead it to the state it was in at the start of The Phantom Menace/the Invasion of Naboo.
1000-19 BBY The Sith remain in the background plotting, but mostly quiet (and some were even content to stay to themselves) until they manage to subvert the Republic from the inside and use it to destroy the Jedi Order.
So, from this timeline we can determine several things. First, while conflicts between Force users
can be devastating, they tend to be more short spurts of battle lasting only a few years, with only three (admittedly large) exceptions. Second, the millennia long conflict between the Sith Empire and the Jedi was pretty much started by the stupidity of three people, Naga Sadow (for leading the Sith into a war with a vastly superior enemy) and Supreme Chancellor Pultimo for ordering xenocide against the Sith (thus leading into the cycles of revenge) and ultimately the Jedi who chose to exile the alchemists from the Second Schism rather than purge them out like the First. Third, while there tend to be a plethora of smaller orders, the Light side tends to be dominant on a galactic scale, with about
18,000 years of Jedi dominance and the large-scale conflicts were almost always between non-Force using groups, before the Sith were even a twinkle in the mind's eye (and of the 7,000 years after the Sith formed about 4,000+ were conflict free with the Jedi being dominant and the Jedi ultimately winning when they did come into conflict [even if it could take them awhile]).
Thus of the Republic's 25,000 years
at most 1,500 were spent with a major Force user conflict going on, and not all of those actually effected more than a few dozen systems at a time. Reducing that back to our own time scale (from first writing to today) that's about 300 years worth of wars between Force users, which puts it about equal to the Crusades from our history.
TLDR: The Light side wins every time, and pure Dark side tends to be the aberration rather than the norm. Conflicts between Force users only become devastating when the Dark side is left to fester, those who fall to the Dark side without building on someone else's work tend to be relatively ineffectual in the long term. The Dark side is more like an infection that only gets dangerous if left untreated or treated wrong.
