These are my opinions, and I have tried to be well informed.
It's not so much about how Trump won, but how Hillary lost.
Millions of voters in middle America believe liberals have left them to rot. And they have proof. There are other factors at work, and critics can't lay this at the feet of Jill Stein or Bernie Sanders:
Billions of dollars in free media exposure for Trump.
Electoral college countermanded the popular vote.
Voter suppression among minorities.
Public's perceived electability of candidates vs. actual capabilities.
Low voter turnout due to unappealing candidates on both sides.
Mysogyny, and the hatred of Obama.
* * * * * * * * * *
Trump has exploited the fears, prejudices, and misery that the GOP has created in the South and the Midwest. Many people there believe the money elites have abandoned them, left their towns to rot, and also coddled other people who are "unworthy". A Trump administration may toss a few bones to these states with infrastructure projects, but will also run up colossal deficits. I believe quite a few people in the U.S. also hope the "unworthy" people will quickly deported... or imprisoned.
This post is grim, and it is meant to be. The idea the pendulum will swing back to the left is obsolete. We also thought George W. Bush was the worst, but conditions in the U.S. will only bring out people like Trump. And worse.