IMO that will be buried ( literally ) so deep that we will never know in our lifetimes, if ever.
If we know who ousted Biden we will know who is running the country. IMO the plan has always been to install Harris ( it was HRC but she is obviously too politically damaged to try again with ), but Biden became so demented that he fell off the program and thought he was actually capable of being POTUS, again, hence them letting him take part in the debate, following which his goose was well and truly cooked.
As always, all above is my opinion.