I'm not buying that Hitler was brilliant at all
He did far too many stupid things to be brilliant, IMO. Politics is an arena where the mediocre can excel. He was a political manipulator, a sociopath, and a meglomanic. One manifestation of his meglomania was his refusal to let his generals conduct the battles because that would be conceding that someone knew more than he did.
Perhaps it's easier to think that he had to be brilliant to rise to power the way he did and to lead his nation into the depths of depravity. It's harder to accept that a former corporal and failed artist, someone not too different from an ordinary person, could do these things. It's kind of like those people who insist that a single mediocre individual could kill a president, but it happened more than once.