So, I think a big part of the pressure for Pete to get out is a reaction to Bernie's performance in South Carolina last night. (Hear me out.) From 2016-2020, after actually investing time in the state, Bernie barely improved his numbers with African American voters. He also lost African American voters in Nevada, but not as badly as in SC. Biden is absolutely right in that you do not win the Democratic nomination let alone the presidency without winning the African American vote. (Which, of course, is not a monolith whatsoever.) I think if Bernie had managed to do a bit better, keeping it actually close, I don't think Pete drops out. Obviously, Biden's strength was like a huge part too, but I think you can't consider Biden's strength last night without also evaluating Bernie's weakness. The only Dem candidate who became the nominee without carrying SC was Edwards, and he only won by 14 points while being the Senator from the adjacent state.
With SC being the first majority minority state (NV was 65% white after all) I wonder if that kinda spooked some folks who, while they probably didn't/don't want Bernie, they would be fine with it if he was improving his numbers with Black voters from 2016.
And let me be clear, I am in NO WAY white washing Bernie's support or saying his performance among Latinx voters is anything less than impressive.