My reading of history is that Hitler failed because he was Hitler.

He was a powerful orator, and also a narcissistic man baby, high on his own self importance long before he was high on meth/cocaine/heroin/etc.

He was too paranoid to trust anyone more competent than he was, and he was fucking incompetent.

I could go on, but in short, Hitler was a conman who tapped into that special hatred that some people have in place of their hearts.