"What's that, you say? We're planning on fully remilitarizing, annexing and conquering our way across Europe, all after blatantly violating the Treaty of Versailles, and Britain just might take exception to that? Preposterous!"
So Hitler was being Hitler, as I had basically said before. He always was enamored with big, flashy, Rule of Cool things, no matter how impractical they may have been.
The real irony is that their greatest success--getting the jump on the HMS Glorious and her two destroyer escorts and sinking all three of them, albeit at the cost of one of the battleships eating a torpedo--came about because the Royal Navy could not into carriers in WW2 (phrasing intentional). (Considering that this came after an almost as embarrassing episode early in the war, where they lost another carrier because they decided it was perfectly fine to send their only two escorts off to go respond to a distant contact report of an enemy submarine, it was something of a trend.) As dramatic as blowing up the HMS Hood in one shot was, Bismarck still took significant damage from Prince of Whales in that fight (despite the horrendous turret problems she had), was promptly torpedoed by biplanes (after said biplanes had attacked friendly ships first by mistake, because Royal Navy), and then finished off without inflicting any further damage to the enemy. And, ultimately, Hood was just a worn-down battlecruiser whose speed was not even impressive by 1940 standards--a respectable ship, but not as valuable as a fleet carrier.
Problem is, submarines could achieve that themselves. So could naval aircraft. The two working together would have been a fearsome combination.
Plus, imagine: French battleship goes to attack a convoy, only to find out that the convoy didn't just have a couple of destroyers for escort: they were escorted by submarines. Submarines who are gleeful that the French battleship so courteously came to them.
