Upside down populism. They project themselves upwards onto Trump; they see themselves in Trump. Trump says the quite parts outloud and justifies it, he gives them easy answers to complicated problems, he gives them enemies to blame everything on, he preys on their lack of education(Ronald Reagan slashed education because the poorly educated are easier to fool and radicalize). Trump is rude, disrespects women and the disabled, he tries to be masculine and intimidating, Trump does what he wants.
Also "If you can convince the lowest white man he's better than the best colored man, he won't notice you're picking his pocket. Hell, give him somebody to look down on, and he'll empty his pockets for you."~ 36th President Lyndon B. Johnson. Trump tapes into this feeling with his supporters to a T.