The left "abandoning" the working class is Clinton telling coal miners "I'll spend $30B on retraining you for new jobs, and building up new industry in coal mining region" vs Trump saying "I'll save your jobs".
Was Clinton "abandoning the working class"? It doesn't feel like it, but it certainly could be construed that way.
OTOH, Trump's statement was a bold faced lie. He didn't save coal mining jobs, coal mining jobs dropped significantly during his first term.
People will take unknowns over the current status. The coal regions are still severely depressed. It likely doesn't matter to those people if $30B was spent if they didn't see an improvement in their own lives from it. Even if you get retrained, you have to leave the area to get a decent job about half of the time, which many don't want.
I think that depends on what Biden/Harris was promising them. If nothing really improved under Biden for them and Harris didn't have a good value proposition for them, then what was their alternative? Neither Trump nor Biden/Harris helped them, but one option is saying they will help them (or is more aligned with their values on non-economic topics).
Was Clinton "abandoning the working class"? It doesn't feel like it, but it certainly could be construed that way.
OTOH, Trump's statement was a bold faced lie. He didn't save coal mining jobs, coal mining jobs dropped significantly during his first term.