And she’s an abject disaster that you cannot u see any circumstances let off script for a second.

She certainly had a mediocre performance as a Presidential candidate in 2019-2020, but I think you're exaggerating. She's not a great campaigner, but many other candidates have been so-so campaigners and still done fine (W is a prime example of someone who had issues with malapropisms and imperfect public speaking, but still got elected twice).

I think you’d be surprised how fast the d’s would transfer any GOTV apparatus to a new candidate. Their dark money outfits like Act Blue are interchangeable already.

Again, there's no "d's" that control the campaign apparatus. Biden controls the campaign apparatus. He's the candidate, they're his campaign organizations and fundraising entities. The $200+ million he's raised has gone into his campaign and PAC's, not the DNC coffers. The days when Presidential candidates relied on the parties, rather than their own campaign committees and organizations, are long long gone. Sure, there are some GOTV and other campaign structures that are run by the party (nationally and by the state parties), and those are important - but not nearly sufficient for someone to just "plug in" and run a real Presidential campaign.

These illusions of another candidate being chosen by some shadowy cabal of uber-powerful party figures (who don't include the actual gol-darn President or Vice-President, apparently) are just that - illusions. Biden is the incumbent President, so he'll be the nominee. In the event that he's unable to serve as the nominee (but still able to serve as President, which is a very narrow window), then Harris is the most likely person to replace him at the top of the ticket - by far. And of course, if he's unable to serve as the nominee then he's probably suffered an adverse health event with a very good chance of making him unable to serve as President - and if Harris replaces him as President, then it is near certain she'd be the nominee.