Because he will go toe to toe with anyone and he speaks the truth!
He also does it with signature New Yorker pugnacity and directness. Flyoverans may dislike New York pushiness, rudeness, and contentiousness in neighbors, tourists and collection agency calls, but they want a President who doesn’t pull his punches or beat around the bush. Trump is it. Hillary may be a nominal New Yorker for purposes of becoming a Senator, but she doesn’t have the New York style. She’s just nasty.