Politico gives even more detail around this.
"Early Saturday, Biden told senior aides it was “full steam ahead” for the campaign. But by later that evening, he had changed his mind following a long discussion with his two closest aides.
Steve Ricchetti, who’s been with Biden since his days in the Senate, drove to see the president at his house on the Delaware shore on Friday. Mike Donilon arrived on Saturday. The two men, both of whom had been by Biden’s side during key decisions about whether to seek the presidency in 2016 and 2020, sat at a distance from the president, still testing positive for Covid, and presented damning new information in a meeting that would hasten the end of Biden’s political career."
I am grateful President Biden finally accepted the reality he couldn't win but let's not turn this into some sort of masterstroke he hatched up. He hang on too long. Ds leadership didn't challenge him last year when they should have and we are where we are.