Kamala was astroturfed as fuck. she didn't poll well when she was in a primary, and had no time to form any connection with voting Americans as the democratic candidate. she spent most of her campaign giving speeches that catered to the 'vote blue no matter who' crowd and simping for republicans while turning up her nose at the progressive crowd (all establishment democrats do this btw)Kamala would have broken that glass ceiling and Trump would be in jail
Ultimately she didn't run a completely shitty campaign, but, as it turns out, Americans like to vote for a candidate that they voted for in a primary. Having their choice selected for them by the establishment is force-feeding. They would also never throw Trump in jail-- Trump was their golden fucking goose for the past three elections, a man so openly repugnant that all they have to do is point at him and say "look how bad that man is" to try and scare voters into voting for them. otherwise, "nothing will fundamentally change". more simping for israel and netanyahu, more soft-ball with ceos and billionaires, and more identity based campaigning.
The democrat establishment likes Trump a lot more than they like the average progressive American