I think there was no plan B because any plan B would have been obviously preferable, thus screwing over Biden, his family, and his advisors. They are what prevented it.
It would have taken courage, and there is no courage in Biden’s orbit. The democratic party need to man the fuck up and coup Biden. Electeds need to publicly withdraw support and force him to renounce the nomination.
If he is fine he has 5 days to prove it, easy as pie. Hold a press conference, do five interviews on TV/podcasts. If he cannot prove it, fuck him.