It's the donors who are responsible for Biden being the 2024 candidate. Their donations to Biden are non-transferable and they won't budge because he is soft on the industries they represent (tech, defense etc). In fact one donor even told the Wall Street Journal "It's a dead horse, but it's our dead horse and we're gonna flog it all the way to the glue factory."
I find this total lack of concern for the good of America, compared with their own corporate interests, to be chillingly inhuman.
Having said that, things have changed again in the last 36 hours since the Trump immunity was announced. We now see very senior Dems, including the lawmakers (a powerful group) and even Pelosi questioning whether Biden should run. Also the New York Times reported yesterday a donor who told them Biden should go. So the tide may be starting to turn. Today's meeting with senior Dems and the Bidens will be pivotal. I note that Newsom and Whitmer will be there.
Jill and the whole Biden family bear some responsibility for their deliberate scheming to hide how bad Biden was even from White House staff. A number of White House staff have been saying this off the record for years and a few came forward on the record this week. It is unprecedented in White House history: it's not like Downing Street, the Pres always has and has always had staff around him to record discussions, take briefings, make briefings at all times. Even under Trump. But with Biden, his family separated him physically from his staff. His Chief of Staff was concerned by this. It is profoundly anti-democratic. More monarchical.
Jill Biden is also guilty of some missteps which smack of arrogance. The Vogue cover this month was incredibly bad timing with the debate. It was just a puff piece. She should have done it much earlier this year or later (if Joe had done well). But posing in a $5,000 dress on Vogue when your husband clearly cannot run the country at a time of high inflation, homeless crisis and unprecedented fentanyl deaths....well, It just smacks of Marie Antoinette. She should have been better advised.
So, I would say that all the people around Biden bear some responsibility. They should have actively started grooming his replacement in 2020. They did not.
The only person I give no agency to is Biden as he is too sick to have any agency any more.