that Biden's shaky performance at the debate was at first blown out of proportion by the media, which couldn't stop talking about it. That kind of coverage had to have influenced people's opinions, evidenced by increasingly bad polls and in a drop in donations, causing further panic among the politicians and the big donors, and the whole thing snowballed out of control. Once the collapse in polls and donations reached a certain point it was probably irreversible. But the reality was that Biden's poll numbers already hadn't been very strong for months, and the poor debate probably amplified existing concerns many people already had about his age. Based on his appearances that I saw on TV after the debate he seemed OK to me, and back to normal. A lot of people seemed to think he was fine - but others were skeptical. I don't think he was ever able to shake the perception, even if it might not have been the reality, that he was getting too old to serve another term as president.
I was pretty unhappy with the way some politicians took their doubts public, but maybe they thought it was the only way they could persuade him to step down. Some might have been motivated by big donors or by opportunism, but others were probably legitimately afraid that he couldn't get his mojo back and defeat Trump. I'm sure he didn't want to give up the campaign since this has been his career for his whole life, but he must have finally recognized that staying in carried a serious risk that he'd lose, and he certainly didn't want to be responsible for another Trump term. So he did what is proving to be the right thing.