One explanation for National Socialism appeals to psychological explanations. Hitler, for example, was an art-school reject and, the argument runs, that trauma led to resentment, which is a major part of why he became a Nazi.
I’m skeptical of that explanation (as I argued here) — mostly because there are thousands of art-school rejects who never became Nazis and millions who became Nazis with no special interest in art or no serious history of rejection.
On the former count, I’m reminded that Auguste Rodin was also an art-school reject. Rodin chose to persist and achieved artistic success independently. Hitler chose another response and another path.