Don't really know a lot about the guy, and his crystal ball skills aren't that relevant to the matter tbh, but I think the guy who shadowed Trump enough to write his book for him knows him better than we all do.
And even if he is/was a successful business man (which is debatable since no-one actually knows his worth) I'm not sure how that makes him suitable to be POTUS.
I'm a successful accountant, doesn't mean I'd be any good at being PM.
Plus then you have his previous Secretary of State calling him a moron...and it's well documented that he is not a man for details, has a short attention span, gets bored easily, doesn't prepare for things and shoots from the hip lip. None of which are positive traits for a politician.