I think you see the "X is Hitler" trope quite a lot in politics. And yes, the similarities are uncanny but there's a very simple reason for that:

All moderately successful and ambitious politicians will, to a first-order approximation, be similar to Hitler. Why? Because Hitler was a successful, ambitious and quite influential politician who fought against the hardships in his life. This is not to say that Hitler was in any way good, but the "similarities" you refer to are quite natural considering that you're comparing classes of people that must (by necessity) have similar character traits. A timid, unambitious person wouldn't be a serious contender for President of the US.

All of this being said, I'm not American so I literally have no ball in this game (though on the record, Trump's policies on climate change are more than enough for me to not wish him to be the next President of the US).

> Because Hitler was a successful, ambitious and quite influential politician who fought against the hardships in his life.

Sorry that's not a 'first order approximation of similarity to Hitler' any more than 'adult member of the human race' is.

A comparison made directly to Hitler would, as a first order approximation, follow the most notable facts about him. In fact, most politicians are not megalomaniacs who rise on a platform of racial scapegoating and then go on to wage total war and genocide. Donald Trump, uniquely among modern American political figures, strikingly resembles the first part of that.