Is this supposed to be some sort of revelation? She didn't get anywhere in the 2020 primary. No one has any genuine enthusiasm for her. It makes no sense that she was VP in the first place.
Sure it does. The Vice President is an almost useless job.
The VP has two tasks under the constitution: Emcee the senate, and be the President's understudy. It's a position that only has power if there's a tie in the senate, the VP gets to cast a tie breaking vote. It's not uncommon to stick a candidate who has some momentum but the party doesn't like there to get them out of the way. Look up Teddy Roosevelt's career to see how foolproof that plan is.
She didn't have any momentum though in 2020. Her campaign was basically dead after Tulsi Gabbard shut her down at the Democratic debates in 2019, she was pretty much done after that until Biden picked her up on the ticket.
If Biden steps away, Harris is the only realistic chance. Various groups would be offended if the VP -- who is also a woman, and is also a black woman -- was bypassed. Further, there is an easy flow of money from Biden to Harris without having to muck with shuffling funds through different PAKs. Lastly, Harris avoids tomfoolery about how delegates must vote if republicans try to go to court about it.
I fear you are correct that Harris is not a favored candidate when placed against other Democrats, but that doesn't matter as much as swing voters in a few states. Sadly, the current polling I've seen suggests those critical voters don't like her. That said, I think she has the chance to come out with a new message for a path forward. Maybe they'd vote for that? I don't know. She'd need to be positive, strong and also to absolutely ridicule Trump.
Side note: I've seen a couple articles suggesting the most progressive dems want Biden to stay while the more moderates want him out because they think it will help in Congress. Samples:
Bernie was gonna take it in 2020 so Carville convinced Clyburn to endorse Biden in South Carolina, flat out stating that he did not care if there was electoral interest past the current election.