One of Biden's biggest mistakes was choosing Harris as his VP, she's been pretty much worthless as a VP, other than doing her tiebreaker votes, but I'm pretty sure anyone in that position would've done the same exact thing. Still though, apart from recent history, VP's have usually been pretty much ceremonial in that role, so maybe it's more a return to form having someone like her there, rather than a Cheney or a Biden actually being considered a key part of the administration.
Biden being a VP was the only other reason to vote for him besides his stated ability to negotiate with Senate Republicans...
They were both bullshit reasons. When a candidate the party likes can't win a primary, they make them a VP and then claim that makes them experienced.
Hell, with Biden they even said that wouldn't happen because of his age, then over a decade later he still became president.
There's an obsession about name recognition, ignorant of the fact that even the most politically disengaged Americans will know both candidates before the general even starts.
she wasn't popular enough to primary him. there was some issues, IIRC, with her history as a prosecutor (of the "tough on crime" sort.) She's certainly more qualified that Trump, or anyone trump would pick as a VP at this point; but I don't think she'd win her own election... even if Biden had worked to set her up to replace him.