That’s likely because most of the Spanish-speaking population here in NYC very proudly associate with their national heritage, e.g. Dominican or Puerto Rican (aka “Nuyorican” for some). So they don’t want to be lumped into a broader term, strongly preferring those national terms. Same with Mexicans and others.
But these are the two umbrella terms used to refer to disparate Spanish-speaking/Latin American descent groups combined into one. So the point is that if you gave Dominicans or Puerto Ricans here a choice on an official form of only Latino or Hispanic, they’d almost all take Hispanic. On the west coast, more Mexicans (for example) would choose Latino.
As for trump, he was briefed by someone in the campaign who was aware there are nuances. But they clearly don’t have a firm grasp of those nuances. In fairness, most don’t.
