Appeal

Trumpism works well as a way to channel hate. When your leader hates the same things you do, he becomes more appealing. He becomes your attack dog.

This is how someone so crass and disgusting finds favor with the electorate. Human psychology's dark side is fed into via grievance. 

Trump says things openly that his base wishes they could which is how his being a dimwit can be disregarded by so many. It makes him appealing to those who felt talked down to by elites who pocketed all that money and left them behind.

What many don't notice is that he is not on their side at all.