The white people voting for Obama were Liberals who epitomize the benign brand of racism, the kind who consider themselves color-blind which, in itself, is a form a racism, the implication being that they don't see black people as black, - as if to do so is to degrade them. Several of my black FaceBook friends tell how the white friends who they once consider unprejudiced, showed their true colors when it came to supporting Trump. Once instance on FB was posted by a black girl telling how she and her white boyfriend broke up after he started explaining why he supported Trump. The same thing occurred decades ago when the reactions to the verdict in The OJ Simpson trial was split right down the middle, divided by race, and the most liberal of whites were right there among the rest of their race, indignant over this black man not being found guilty of killing a young, blue-eyed, blond white woman..
As for being stupid, the bulk of white people voting for the "Republican" Trump, as astute observers have noted, were stupidly voting against their own interests under the guise of making America great again, and restoring the freedom to indulge their bigotry. Blacks who went for Trump were sell-outs voting in their own self interest, hoping for personal gain by doing so, or those who were bamboozled into thinking Trump would solve black problems, or were simply people who chose to cut off their noses to spite their faces since Bernie didn't get the nomination..
Of course there are always truth tellers who transcend race such as white news commentator, Bill Moyers, who wrote a very insightful piece, echoing what Toni Morrison said about Donald Trump's success being the result of white people fearing that their white skin was losing its value, and in danger of being obscured by people of color, and who wanted to regain and fortify their white supremacy status, putting the power back in the hands of white rich men where they think it belonged.
Actually, xenophobia and racial bias are natural to people with a tribal mentality so what I opine is not necessary an indictment of those who are loyal to their own kind. It's the way of the world. It's just that poor ol black folks have never secured the opportunity to gain the upper hand that would enable them to rule over and oppress white people.