Could have been both. Biden in bad enough shape during the election year that they had to hire a stand-in, then never fully recovered but has been in good enough shape to appear from time to time, then they (some of them, maybe Pelosi) don't trust the stand-in well enough to fully replace Biden so as Biden's mind got worse they decided to get the stand-in out - or alternatively the stand-in, or the main actor of a few of them, the one who has been the only one good enough to actually play Biden, decided he has had enough and maybe even already left - and maybe now it is just Biden himself.