Indeed, of course, when Hindenburg asked Hitler to form a minority government, Hitler wasn't a mass murdering dictator either, just a purveyor of sketchy ideas based on emotion rather than ordered thought. This summer may see an even stronger analogy between America and Weimar Germany if the Trumpists take to the streets, in which case we'll have left-right street battles between them and the BLM types analogous to the Nazi-Communist street battles in 1920's, early 1930's Germany.
There are distinct socioeconomic similarities between America today and Weimar Germany, and those are the real cause for concern. A person who could have been a Hitler would not have reached that pinnacle of evil without the fertile situation in which he developed, they would have been a mere footnote instead of the subject of libraries.
But because the poor economy, high unemployment ("low workforce participation"), a ready-made scapegoat class (welfare recipients, invading illegals, and 'refugees'), the perception of lost military effectiveness due to mismanagement at political levels, the slide in national prestige on the world stage, and the question of national debt, all exist, one who promises to solve our ills and take care of the undesirables, to put the country back to work, and improve the economy (while beating the Communists!) will indeed receive a great deal of support. Perhaps far more than they should, and there are plenty of mechanisms in place by which an already largely nationalized police force and myriad agencies can impose totalitarianism without passing a single new law, just ignoring some fundamental old ones.
Human nature says that as long as those abuses are aimed at the targets of the majority's angst or anger, the abusive nature of those actions will be ignored or encouraged, and the cries to quash such dissent as may appear will be shrill, indeed
Comparing any politician now who isn't a full blown totalitarian with someone with the power and existing mechanisms to just dive in and start extermination of entire subgroups would be folly. (Sorry, once you enter the arena, you become a politician, regardless of your old job.)
What makes such difficult to spot is that it must be done in a far less developed, almost larval stage, not as a fully developed entity. It is the bad seed in fertile ground that burns whole continents.