When there was a PR blitz for a week, where several figures were saying "If you see Biden behind closed doors he's as sharp as a tack!"; I interpreted that as confirmation Biden was experiencing cognitive decline.
He conceded to what was essentially a coup, allowing Kamala Harris to take his place in the General Election, likely because he just didn't have the stamina or the fortitude to mount any sort of coherent campaign.
What I saw on the ground during early voting was that this move actually suppressed Democrat turnout. Compared to previous early voting periods in my county the Democrats were missing a substantial portion of their early voters. The mid election swap destroyed their enthusiasm.
Without going through a Primary process, Harris never had the opportunity to build her on organic base. It's also unclear that she would have won the Primary in any event. Harris essentially was the designated loser against Trump.
I don't feel bad for Harris, not even a little bit. Everything that is happening is self inflicted.
Biden turned out to be incredibly selfish too.