No, I'm not attempting to rewrite history, Boson. The parallel with Trump, I suspect, lies in the ineptness which seems to have characterised Hitler's 'leadership' strategies.
All the detailed research into Hitler's rise and rule is tending towards an image of - as you say - a "penniless, virtually vagrant, angry youth", but whose gift for oratory far exceeded his ability in virtually every other arena. Through the gift he was able to persuade, charm, and incite (see the similarities?) but once he'd become the total ruler of Germany those who'd gone along for the ride started to vie with each for his favour. They were also a manipulative, poisonous bunch and possibly much worse, in fact, than Hitler, but they lacked the direct "appeal to the common man" which characterised Hitler, (again, similarities. Trump supporters almost seem mesmerised when asked why they voted for him.).
But the detailed research is uncovering some truly horrific aspects of the culture over which he presided. For a start Hitler would assign the same jobs to two or more people, who then competed to try to win his approbation in the most heinous ways imaginable. He didn't stay on top of things, preferring to swan around in the limelight while his subordinates fought amongst themselves. He created four offices for himself, instead of one, so it was never clear what was happening. The appalling policy of eliminating the disabled was one consequence of this rampant mismanagement. A letter arrived at one of his offices from a father asking permission to allow his severely disabled baby to die. This was put to Hitler by a subordinate, but only as a passing comment. When Hitler seemed to agree, it became policy and extended to all disabled children, where the murders were carried out by the staff on what amounted to a whim.
Hitler's main thrust was anti-semitic. He blamed the Jews for everything, and an often quoted comment that out of 4200 lawyers in Berlin, almost 3700 were Jewish forgot to note that many professions were in fact closed to Jewish citizens.
So yes; the result of Hitler's dominance was pure evil but although I don't doubt he was an unhinged and possibly psychotic individual I suspect a lot of what happened was more because of his subordinates, who saw his lack of effective management and simply took advantage of Hitler's incompetence. I don't see Trump as competent but I do see a lot of hangers-on, and if the management is poor Hitler's rule shows what can happen.