Personally I believe it's the closest thing to a 'Peasant's Revolt' that you can get nowadays, akin to Brexit where I am.
Mostly I think it's lingering damage from the crash of 2008 that's been allowed to fester and ferment, with much of the economic damage being absorbed by the lower rung of society in terms of quantitative easing. The decimation of savings and land value hamstrung those mostly asset wealthy, houses and land, outside of the cities, which combined with the upswing in globalism luring traditional industry away with nothing to replace it pairing together to make a noxious breed of 'FUCK THE ELITES.' as much of the mid-heart of the US, and north in the UK all but bled out slowly. This certainly wasn't helped by the evergrowing gulf of pay disparity, where the
gulf between wealthy and poor is growing to such a degree that it's approaching levels of serfs and lords anyway.
Effectively Brexit and Trump were the first chances of a fed-up majority rebelling against what they see as the upper class; to get a sense of power and burn the castle down. Is it wise? Probably not. But unless something is done to really even things out in terms of resources, spending power or being able to attain life goals with some sense of fairness, it's not going to go away.
Look across Europe with the absolutely swelling support behind nationalist parties, England, France, Italy etc etc. It's going to fracture the land in more ways to come, and get worse. The feeling that we need to 'fix' our home first, before helping other people, that the country is 'broken' somehow. It's a society that feels powerless and forgotten, regardless of how true that might be.
The ride never ends.