Hitler might well have had to have been replaced for the Nazi state to have held onto power if it had won the war.
Why? I never saw Hitler as particularly idealistic and unsuitable to the reality of a government wielding power and practical politics.
Because the German people would eventually notice that the Jews were gone, and yet they still had all the problems Hitler had blamed on the Jews.
My take on some historical religious/social/political movements:
The best strategy for complex social movements is not honest rationality, because rational, practical approaches don't generate enthusiasm. A radical social movement needs one charismatic radical who enunciates appealing, impractical ideas, and another figure who can appropriate all of the energy and devotion generated by the first figure's idealism, yet not be held to their impractical ideals. It's a two-step process that is almost necessary, to protect the pretty ideals that generate popular enthusiasm from the grit and grease of institution and government. Someone needs to do a bait-and-switch. Either the original vision must be appropriated and bent to a different purpose by someone practical, or the original visionary must be dishonest or self-deceiving.
There are exceptions to this pattern that, I think, prove the rule when you look at them more closely:
And then there are just exceptions:
One interesting aspect of the pattern is its hysteresis. Once idealism has been successfully co-opted, the resulting organization can continue to siphon that credibility indefinitely, while dismissing its more radical demands.