Lemme take a crack at this…and add a few personal comments afterwards.
The Hitler parallel is accurate, though obviously not to the same degree, so far as we know at this point. Hitler’s National Socialist Party came to power because of vast discontent among the general German populace, which was in a far worse situation than we are today. The allied victors of WWI put Germany under a draconian thumb that heavily impacted its economy (with the exception of the US, who disagreed with this course of action but, being Johnny-come-lately, had no real power in determining the parameters of the post-WWI peace). The response of the Germans was to grasp for anyone who promised a return to national pride and economic health, which is exactly what Hitler did in order to get elected.
Trump is saying the same thing, though it’s generally what every challenger says about every incumbent they face: “Things are bad now, but I will make them better.” But the parallel goes beyond that. No matter how much he tries to disavow or dance around some of his statements of policy, Trump is both racist and sexist and a deluded megalomaniac, like Hitler was. And part of the Republican party is eating it up, because they think that anything would be better than a hated Democrat controlling the White House for four more years.
Unfortunately, this is essentially the same faction of the party that elected Dubyah twice, and we all know how well that worked out.
Fortunately, Trump is proving himself such an idiot and alienating so many moderates and undecideds that, while he may win the nomination, he has absolutely no chance of winning in the general election. Mark my words: people will come to the polls just to vote against him.
Because (and I am certain this has been said many times before) Trump would be a grave danger to the world were he to be elected to the most powerful position on Earth. Only the most deluded among Americans would trust him with the nuclear football, and it seems the overwhelming majority of those are Republicans, who are allowing their party to be made a caricature of itself.