Trump is seen negatively because he can't deescelate any situation. He doubles down on the dumbest, most easily disprovable stuff. His narcisism runs deep so it's easily taken advantage of by folks with nutjob agendas like Bannon and Flynn.

Honestly he's more of a King George III than Hitler. Hitler had much more of an agenda, backed by a competent team, than Trump has. Trump's a 2-bit narcissist that's attracted crazy dead-enders. The threat is a combination of fringe politics, insanity, and incompetence.