I watched an interview Jordan Peterson did recently with a disaffected Trudeu MP. One of the things that he mentioned in passing was around how significant contempt is as an emotion - in marriage counseling, when you see something like one partner rolling his or her eyes at the other, 90%+ of those couples will be divorced in a years time.
Contempt is just a totally fracturing emotion in any relationship, almost impossible to come back from.
I think that across many countries, the progressive left have given a strong sense that they have contempt for anyone who does not share their views, and also people in certain categories. Working class men being a major one. Religious people, specifically Christians.
Part of the reason Obama was as successful as he was, was because he didn't make people feel that way, in fact he very much played to the opposite - (his performance this election was shocking because of how he abandoned that.)
But HC really came out with arms swinging with the whole contempt thing, and I don't think the Democrats have recovered. Harris I don't think has fallen into that trap to the same degree, but also hasn't managed to shed that.
Part of it isn't down to the official candidates either. It's the sense the left media, and the people like this, the professional middle class managers and such, give to all of those who they encounter who don't have the right beliefs and also, right demographic characteristics.
Recovering from the sense that the liberal managerial class despises them will be very very difficult. People don't forget that, and you can't argue it away with policy either.