I just don't think we know everything everyone was seeing or doing. I doubt a bunch of D lawmakers woke up and decided that for this country to defeat fascism, President Biden needed to step down without any data to back it up. Those Ds were probably seeing internal numbers, hearing from constituents, and yes hearing from donors, that indicated every branch of government was at risk of being won by the fascists.
The question is - how hard were folks trying to talk to President Biden privately versus just making statements publicly. Much like most things the story is probably somewhere in the middle. Some people did try to talk to the Biden campaign and were unable to break through but many did not try hard enough and just released a statement.
In the end I think D lawmakers and President Biden wanted the same thing - to ensure that Ds had the best chance possible of beating Rs in all branches and levels of government in November and they all became convinced the best way to do that was for VP Harris to take up the mantle of the presidential campaign.
As hard as it was to see President Biden go through this, so far it seems like it was the best thing for him to step down. Ds are able to go on the offense now because they are not stuck defending President Biden's abilities. Beyond that, even though his speech last night was emotional, it had the hallmarks of all of his recent campaign appearance - halting speech, jumbled words, etc. Seeing him like that just reinforced to me that he needed to step down for the good of country and party.
If I am angry about anything, I am angry at BOTH other D leaders and President Biden and family that this wasn't seriously addressed a year ago. The second President Biden indicated he MIGHT run again several people needed to have a come to Jesus moment with him AND he needed to listen to it.