From Alice Miller, "Adolf Hitler: How Could a Monster Succeed in Blinding a Nation?"
"It was in large part owing to Hitler and his history that I became aware of the dangers of our traditional morality. We are exhorted to honor our parents and never question them no matter what they have done. Yet when I realize that millions of human beings had to die so that Adolf Hitler could keep his repression of childhood trauma intact, that millions were subjected to humiliation in concentration camps so that he never had to recognize how he had once been humiliated, then I believe that one can't point out these connections often enough in order to shed light on this unconscious production of evil. How should young people be expected to recognize and reject inhumanity and crime if these continue to be disguised instead of being pointed out as plainly as possible? Only when young people are permitted to know exactly what happened and how it could happen, only if they don't allow anything to stifle their curiosity and are not afraid of the truth, can they free themselves from the burden placed upon them by their forebears' blindness."
I can't tell if your example was meant to agree or disagree with me.
But although Miller's hypothesis is full of holes, loose ends, and self-contradictions, even if it were true, it neither confirms nor disconfirms the topic of Hitler's alleged lack of self-confidence -- being mistreated as a child and *repressing* it as Miller claims is not synonymous with maintaining a low self-confidence.
If anything, her description of someone who has "totally repressed" childhood traumas (and Miller describes *all* German childrearing of the time as "destructive") only bolsters the idea of someone maintaining an adult self-assurance (since to hold a low self-regard would be to accept and dwell on the childhood disapproval, not "totally repress" it as Miller claims).
Even if that was the motivation for Hitler's megalomania -- and I don't buy it -- the fact remains is that he was supremely arrogant, *not* self-doubting.