The clearest statement I've seen, and that makes sense to me, of what the Democrats / liberals did wrong, that created this backlash is here:
Trump Won Because Leftist Political Correctness Inspired a Terrifying Backlash
The most salient paragraph or two (at least for me - I added the bolding but not the italics):
"...
Trump won because he convinced a great number of Americans that he would
destroy political correctness.
...
What is political correctness? It's notoriously hard to define. I recently
appeared on a panel with CNN's Sally Kohn, who
described political correctness as being polite and having good manners. That's fine—it can mean different things to different people. I like manners. I like being polite. That's not what I'm talking about.
The segment of the electorate who flocked to Trump because he positioned himself as "an icon of irreverent resistance to political correctness" think
it means this
: smug, entitled, elitist, privileged leftists jumping down the throats of ordinary folks who aren't up-to-date on the latest requirements of progressive society."
The thing about this, is that both points of view are right, from the point of view of the people who see the world the way they see it. This election result, IMHO, should strongly suggest to people with the former POV (being polite and having good manners), that there are a whole bunch of very angry people who see it very differently. Differently enough to have this define how they voted, and in enough volume to move a very large election.
Angry enough to vote for somebody who (also from the linked article):
"Nobody votes for Trump or likes Trump on the basis of policy positions. That's a misunderstanding of what the Trump phenomenon is."