This is some of the best analysis I've heard, actually.
Trump is not a great businessman. But he hasn't had to be, because he's a great brand ambassador. Branding alone is where Trump has made most of his money. Slapping his name on things. Nevermind that he's a failed real estate developer. People associate his brand name with greatness, and that makes
OTHER more successful developers want to attach his name to their projects. So while Trump sucks at creating brick and mortar things, he has been great at cultivating his image, which he sells at a tremendous premium.
Same goes with his candidacy. He's an idiot with no understanding of foreign or domestic political and economic issues. With that being said, he's also quite savvy enough to know that
MOST AMERICANS ARE ALSO IDIOTS. So he appeals to their ignorance, appeals to their fears, uses simple slogans that are easy to remember and slaps his name on everything. And it's worked like a charm. His followers stay easily on message, because he doesn't clutter it up with facts. They like him because he's a asinine and ignorant as they are. He is a representative of American pop culture, which is impressive given his age. He's a branding expert running against a bunch of lawyers. They can argue issues till they're blue in the face, but his message will cut through that clutter every time because he don't care about being right, he only cares about promoting his brand. And that's what Trump does best: promote Trump.