Gradually, but especially over the past 8 years, the Democratic party has changed from standing up for the little guy to using identity politics to triangulate on one enemy. According to the DNC, that enemy is the source of all of the evils in the US and they intentionally pitted as many different groups of people against that one enemy as possible.
That one enemy is the White, Christian, Heterosexual Male. Trump knew this more than anyone. He saw that White, Christian, Heterosexual Men realized decades ago that they were being sold down the river by the GOP by keeping the borders open in order to continue to exploit illegal labor.
The GOP gave them Romney and McCain and basically told Blue Collar and poor Whites to pound sand. The GOP flooded the field until they could get the numbers to usher in another Bush. Then along came chump.
Chump basically said, “Vote for me and we’ll put a stop to this. In fact, I’ll build a wall and make Mexico pay for it.”
All the other groups played Identity Politics against White people, even though it is tearing the country apart. Well White people decided to do the same thing, even though it will tear the country apart.
Hate the mainsteaming of White Nationalism? Blame Barak Obama and the DNC. If they had chosen unity instead of triangulating on and demonizing White folks, we wouldn’t have this crap.