She was basically trying not to go negative on Biden while still in office. Biden and his team were actively pressuring her to stay onside, according to some reporting, which is indefensible. Reprehensible really. She should've burnt the bridge.

But it probably wouldn't have made a difference in the end. It was all mostly over when Biden decided to run again in the first place. Kamala moved numbers in states she campaigned in, and she probably could have moved more with enough time.

Mistakes were made - but most important and most blameworthy mistake came from the Republicans 4 years earlier, when they rejected their obligation to impeach and convict after Trump nearly killed them all on TV.