I grew up with the impression that Vice Presidents often become the next President, I guess simply because of George HW Bush. But it is more common for a VP to take over because the President died than it is for them to get elected as the successor.
It has been very interesting to watch all the weirdness of it. There seems to be a surprising handicap for Kamala in it. Donald Trump gets to run as if Kamala were responsible for everything Biden has done. He and his supporters can think of very little that Biden did right, except continuing some of his policies, so it amounts to blaming her everything that is wrong even though she was the Vice President. BUT watch what happens if Biden lets her step up and act like she is President. DeSantis says she's never done any of this and she is only nosing in to look Presidential. Cool trick, huh?
Kamala and her supporters see lots of nice things to say about the Biden administration, but Kamala can only take the small, measured credit of saying she's been proud to be working with Joe. Otherwise she'll be glory hog. And when someone asks her about a failure, she can't say "Yeah, Joe dropped the ball on that one" or she'd be a backstabber. So she can't take much of the shine and can't drop any of the stink.