Has he really hurt his brand? What exactly was his brand before this? His net worth is so tied into his branding, a vague notion of what his name is worth. This campaign has been a way to monetize that brand unlike anything he's ever done before. Yes he's sold books and had The Apprentice and such, but he wasn't really known to stand for anything. ETA - The Art of the Deal is old news, the Apprentice has been gone for years. He needs a new cash stream. It's like the Kardashian family....they have money, they're famous, but they're really just famous because they're famous. Now Trump has a legion of people who will throw money at him and eat up whatever he has to say.
I would speculate that many Americans have a more negative view of Trump than they did in, say, 2014, but Trump wasn't making money off of those people. But now there's a segment of people who have a much more positive view of Trump than they did in 2014. He wasn't making money off of them back then, but he's sure to make money off of them now. Books, speaking engagements, paid TV spots. He has basically cast his lot to alienate a decent percentage of Americans in exchange for monetizing his name with the remainder of them. I won't speculate as to his motives for running for POTUS, but he stands to make a ton of money if he plays this right.