I agree that people are stupid for not understanding how terrible Trump was and will be. However, I think a big problem was that the DNC didn't provide an attractive alternative to excite these dummies.
There was very obviously support for Harris early on when the DNC made some progressive decisions. Getting rid of Biden was a progressive choice. Choosing Tim Walz was a progressive choice. The DNC was immediately rewarded for these progressive choices with $1 billion in small donor donations.
The DNC got arrogant and decided to aggressively move in a conservative direction. Harris started talking about how she would build the wall and prosecute immigrants. The DNC welcomed the Cheneys with open arms. Harris told interviewers that she would be more conservative than Biden by accepting more Republicans in her Cabinet.
The DNC actively threw away their progressive supporters and gained absolutely nothing in return because the voters they were courting would never have voted for Harris anyway. Racists gonna vote Trump. Moderate conservatives gonna secretly vote Trump. People who want Republicans in a Presidential Cabinet are obviously gonna vote Trump.
If the DNC just focused on stuff like being pro choice or going into detail about fighting price gouging, that would have been much more successful than trying to attract the mythical "Moderate Conservative".