You have to understand the Republican base. They've seen a black man get elected president twice, a woman about to replace him, gays getting married, the USA getting more secular and more brown. Their reality is collapsing. They've also seen the middle class in trouble, and they choose to blame that on the brown people and mysterious unnamed liberal government regulations, instead on the people who are actually taking their money.
Enter Trump. He gives them hope of restoring America to the point before it all went to hell, in their eyes. Something is wrong, the dirty liberals are at fault, Trump now says he hates the dirty liberals more than anyone, so he's their guy. To them, it doesn't matter how he's flipflopped on every issue, or that he makes no sense. All that matters is that he now says he hates liberals more than the other candidates. Look at jknow up there, proudly supporting Trump solely because he supposedly pisses off liberals (though the liberals are actually laughing). That's the sullen teenager attitude the defines the Republican base now, and Trump taps into it.