Rubio’s loss is not that complicated. He betrayed Florida voters on immigration, and he was selling a warmed-over, fresh-faced variant of the establishment’s George W. Bush politics: explicitly pro-immigrant, pro foreign adventures, pro business (including outsourcing), and contemptuous of the interests of the white working class on trade.
His Cuban heritage was the least of his problems, and it would not have been a demerit if he had authentic, nationalist positions. But he also does this thing that is extremely annoying. He tells his personal story by focusing on his immigrant parents, and imagines the best American story is the immigration story, as if legacy Americans that fought at Antietam and on Omaha Beach are somehow less American than newcomers, and, further, as if America can only be its best self if it’s constantly erasing and reinventing itself Etch-a-Sketch style. People that want the basic contours of the nation to remain the same–that is to say, people who want to conserve the nation–are somehow treated as less American than the newcomers in this revolutionary view of immigration as the defining characteristic of America.
The politics of ideology are being replaced by politics of identity. The former are an artifact of an ethnically unified nation. Whites rallying to Trump are looking for someone to stand up for them in some way. Rubio never conveyed the interest or willingness to do that. In addition, he was mechanical, lacked gravitas, and was very beholden to the donor class. For them, he was probably a more competitive choice than the charisma-free Jeb, but only barely, and, this was not his or that failed establishment’s cycle.