You have to hear the recent Pelosi interview.
I saw something similar with other democrats - blaming Biden
But I see this as damage control. Biden is old and his career is done. He's the scapegoat but Harris still have some political career left.
They were supporting Biden and were denying his incompetence until he messed up in the Presidential debate and that assassination attempt.
And, then they forced him out. Even if you hear Harris interview on Fox news (if I remember well) then she was saying Biden is really competent even now but there is sudden switch on Biden after election.
Yes Biden also holds the blame as he wanted to run for the second time but what I am saying is they all were into this and they all together forced Biden out only when it became clear Trump will win after assassination attempt