The easiest explanation is that they are slowly but surely admitting that Joe is demented and it was Kamala and Pelosi who were to become President and VP all the time.

However, something is telling me that Joe is not who we believe to be. He might be under White Hat control or just starting to negotiate with Trump (sort of a plea deal, for example retire to a tropical island instead of being executed) and might be sabotaging the [D] Party regime from within, giving information on his (former?) handlers and preparing to quietly slip the military and DJT back into DC?

If he was just demented there would be no reason to remove him, as he would be useful for signing EOs prepared by Kamala without reading them himself and distracting the public.

Remember that we are all in a movie, so Joe might actually not even be the Joe who was Soetoro's VP but an actor.

TL;DR: either Joe is rebelling and changing sides, or he is under White Hat control all the time