I think they had figured most things out, but Biden going to Cleveland instead of Milwaukee or Phoenix or even Las Vegas the day before the election was a significant error. It seems like Biden's people thought he had more comfortable leads in AZ/NV than he actually did. I don't know what they were seeing in OH, but it was odd because they clearly picked up on PA and MI being closer than public polling.
Trump's camp clearly spent too much time being worried about Florida while laughing off Georgia. The aggressive MN/NH spending eventually stopped, but it could have been better deployed in NV and AZ. The Trump campaign event in Newport News, VA was dumb, but not as dumb as Biden in Cleveland because it was September and he did improve notably in nearby parts of NC. Both sides behaved like the September/October Biden polling lead in NC was real, which you could either say was a waste of time when Trump should have been in Georgia/Arizona or that his campaign did just enough to save the state.
I agree. In retrospect, Joe Biden should have campaigned in North Carolina at the end. If he did that, he would have won with the 321 map and maybe pulled weak candidate Cal Cunningham over the top as well.