Secondly, tribal behavior is strengthened through sports teams, college allegiances, rep vs dem party lines and many other things, with the latter of those being the main reason.
Thirdly, the dems were very pro zionist while Trump was able to maintain deniability. This swung a lot of dem voters.
Lastly, Kamala got something like 0 votes in the primary. Wishing she would win the general election was delusional. Dems should themselves in the foot twice vs Trump with Kamala and when they betrayed Bernie to help Hillary.
You should engage in some critical thinking yourself instead of blasting your insecurities over the internet. Your media diet (bet $1000 that reddit is a big part) needs a do-over.