Honestly? They think both sides are acting like children.
BUT, the left is the side that claims to be the "good guys" with their honor and respect and decency. All that's pretty much out the window with this election.
On the one hand it doesn't seem quite right: Trump is a nasty guy, he'll insult and go after people, he's been inappropriate, so why not go after him? But again, an eye for an eye makes the world blind. You're above that sort of thing or you're not, and the left has not been. At that point it's not clear good vs. evil, it's just side A vs. side B. And the left wasn't strong enough to overcome Trump's messages of change, the same kinds of messages Obama gave in the face of McCain in 2008.
Your average person isn't stupid. And even if they are, they at least understand the difference between a good person and a bad person. And people want to see bad persons get what's coming to them. All that stuff OP listed, it came back to bite them in the ass when Trump was elected.
That's not to say he won out of spite, but again, everything Trump supposedly represents - greed, nastiness, being a liar, no shame, toxicity, not caring about the average man, hell, even racism and bigotry - the left has shown themselves to be capable of this time around.
Frankly, I really believe that gave Trump the edge. Hillary's camp thought she had certain groups and areas in the bag, had a certain sense of smug superiority about her, and just didn't do enough to prove that she was a good choice rather than Trump being a bad one.
Normal people saw Hillary as more of the same and saw Trump as being capable of change, for better or worse. So he won. And the more the left doubles down and refuses to acknowledge the situation, the more they'll end up failing. Sure, in New York, L.A., D.C., you'll have these big giant protests. But in Bumfuck, Iowa where average people work and live, they see it as accomplishing very little.