As I said in another thread:
How do you win 81+m votes despite losing house seats in the bluest of areas, like New York and California? How did the down ballot races not translate anywhere close to Biden’s votes?
I can answer this one.
People like me voted 3rd party for president because both main parties put up duds. Yet down the ballet there aren't always 3rd party candidates, or at least not a 3rd party I'd vote for, so I voted republican.
There are also "Romney" conservatives who voted against Trump but for most other Republicans. A few members of my conservative friends and family said they did that.