You cannot reproduce the backstory of Exalted in the system. You never could, in any edition, but in 3e they've explicitly gone on record saying they're not even trying. That time is done, and over, and such as its like shall never again grace Creation. "Does this fuck up the Usurpation Y/N?" is a very useless metric in 3e. No one in power cares. Nor do the testers, frankly.
So why should I play Exalted? The entire draw, mechanically, for Exalted, is that its core game engine at least
tried to pay lip service to the idea that it was how the world worked. If we're abandoning the idea that the game engine is subservient to the setting and a statement made by the mechanics is, in fact, stating
something about the game world, why am I playing Exalted instead of D&D 4th Edition reskinned to pretend to be Exalted?
Exalted, for me, and for a lot of people, is about being more mature in D&D, both in setting (and I mean actual maturity, not TITS AND GORE 'maturity') and in storytelling. D&D, like a lot of RPGs of its era, distinctly separate 'the game' and 'the setting', and this attitude means that oftentimes interesting settings suffer because they aren't allowed to acknowledge that 'the game' impinges on the setting. The reason I like games like Exalted is because they recognize that. The game
tells you things about the setting. Nobilis, too. Jenna Moran was the absolute master of using the game mechanics to make statements about what the world was like, and although the Ex3E team might not be Jenna Moran they could at least try.
Because if you're discarding the idea that the Usurpation should be at least within squinting distance of the rules-as-written, why keep
anything else? Why do you need 25 Abilities? The rules don't need to reflect the setting, so there might be 25 constellations reflecting 25 skills, but why 25 Abilities? Why 9 attributes? Why have training times? Why are Solars stronger than non-Solars? After all, the rules don't need to reflect the setting, you can have all Exalts being of equal power, or Solars being the weakest, or
anything as long as you wave your hand and say 'it's fun'.
"The rules don't need to reflect the setting at all" is a rabbit hole that goes very deep, and the end result of looking at the game like that gets you Exalted: FATE or Exalted: ORE.
It was impossible to have the Usurpation in 1e. The Primordial War, too. It was impossible in 2e -- 2e tried harder, but that was a horrible failure, because you cannot convey those heights of ultimate power beyond all reason without warping the system around them.
Only insofar as 'you needed a ton of attacks to kill someone due to stacked defenses'. It could have
theoretically happened because there were no charms for escape-death-guaranteed or the like, and Roadie already mentioned that ignoring most of the Ess 5+ Charms it would probably have been possible in 2E.
Early 2e, a paranoia-OK Twilight reactor could slaughter an arbitrary number of Dragonblooded on his own. And other Solars. And pretty much everything else. It never really worked. The Primordials, if you use their stats and Charms, have absurdly high pools that skew the mathematical probabilities so far in their favor you'll never hit, let alone hurt or kill.
Yes, and Jon Chung, the guy who invented 'Usurpation-OK' as a term, was on record as calling them
bugs, because they didn't allow the Usurpation to happen. The developers acknowledged this and here we are.