My analysis (Public Board)
Biden won't step aside voluntarily because that would be the end of the family business of influence peddling. A lot of big money donors may not fund his campaign after that debate performance because there is no doubt that Biden is unfit to run and he's going to lose.
The dems never should have waited so long to get rid of Biden if that was the plan. They have all known for a long time he is a cognitive mess. It doesn't seem right to me that they allowed him to participate in that debate in that drugged up, weak condition. I expected to see more of a jacked-up Joe.
It does look like Biden was set up to fail at the debate, but its kind of late to swap out the candidate. If they go with the 25th amendment approach it will be ugly and messy and then you have the Kamala problem. She is not happy that she hasn't been considered as a replacement for Biden. Its just a train wreck for the dems all the way around.