A primary explanation would be that they voted out of anger--less for Trump than against what had happened to them and against the people who had let it happen and essentially didn't care. They were angry because they felt diminished, reduced, disrespected, ignored. Trump was the anger vote. Without this anger a lot of the energy around Trump would never have gathered.

It is impossible to forecast exactly what the outcome of Trump's victory will be.  In my own view, the biggest threat is to democracy itself. Trump is nothing if not authoritarian. And a polarized population is not in a democratic mood. Not many people have taken democracy seriously lately. It's not at the top of the list of most social activists who already have the answers and don't need democratic processes. And the study of democracy is not exactly required in college. And that's part of the reason we're in the situation we're in. 

There is a huge amount of work to do.