He got the nomination by promising to make Mexico pay for "the Wall." And all the Pubs fell in line when he did. Almost all of them, anyway.
Your latter point is perfectly circular. If I say that Bernie was harping on things that would be liabilities for her and that cost her the election, it is literally no answer to say, "everything he called out was borne out in the general." Hey, maybe he shouldn't have been calling them out.
For all you like to champion the authentic experience of the middle class, you have an odd view of how they consume politics. People don't just hear something once and respond to it. It's when they hear it over and over that it sticks. That's why we talk about amplifying messages. If Bernie had not been amplifying the "HRC is corrupt; we have a uniparty" then I believe she would have won. THAT is why I came to dislike the Bernie Bros. Not because I thought they were wrong about everything, but because they were more interested in purity than winning.
To his credit, Bernie -- though he evidently fucking hates Kamala -- did not take any shots at the nominee this year or in 2020. He learned. And some of the anti-HRC stuff may have been sparked by him but really carried through by his supporters. It wasn't Bernie who Sarah Silverman said was being ridiculous.
Anyway, when I want to figure out what motivates voters, I think it's useful to start with the things they chant relentlessly at rallies. When they go to rallies dressed up like walls, and chant Build The Wall non-stop except when they are chanting "Lock Her Up" -- I don't know. Maybe those are the things that are exciting them?
That's my major problem with your analysis. It's like you didn't watch anything that happened in the campaign, or anything that Trump supporters say on a regular basis -- even on these message boards. I know you did. I know you know it. I just don't understand why you discount as if it's meaningless. The idea that "well, if we gave them something to be excited about in their lives, they wouldn't turn to hate" isn't implausible, but it's not convincing given the relative paucity of the evidence supporting it.