Then let's look at his record in this regard. We see him leaving a slew of failed business behind, businesses he owned, while continuing to personally enrich himself. Expect no difference if you put him in charge of the country. He won't give a shit about the USA, just what is in it for him. That is his modus operandi, and you have to be blind, almost willfully so, not to see it.
But it's a stretch to say he don't care. If things begin to fall apart as president (oh say, an immenint impeachment), then yes, survival mode kicks in and America doesn't remain his number one prority, but to think he'd get in and not care very much about bringing his genius to bear on making the US prosper like never before is a bias bread on bad reasoning.
There may be many things in the past he has done that he wouldn't do as president. You can't live by the saying, "once a thief, always a thief." People of a particular caliber cannot be properly judged by track record. I think he is fantastically full of crap, but to say he won't care when put in the position to effect great change is not even remotely guaranteed by his actions of past roles.