I'm surprised they're turning on him and raising the issue at all. He didn't seem substantially worse than his 2020 campaign run and Axios (I think) had already floated the "staffers privately tell us he's senile" piece earlier in his term but it didn't seem to stick. His current state can't be a surprise to power brokers so why hang him out to dry now?

I suspect they're trying to avoid a primary. The 2020 election showed the average democrat voter is too dumb to pick up on media hints to the insiders' favorite candidate and the average well-established democrat is too greedy and delusional of their own personal brand recognition to step aside. The pipeline of "chosen ones" that can be legitimized without much pushback at the convention seems empty.