It's occurred to me recently that Biden has a zugzwang on his hands. That's a chess term which in German means 'compulsion to move.' Basically, a person would like to pass on their move if they could, but they can't. So by moving, they make their position weaker. Like at the end of a game, a player has a king that's guarding a pawn. The only choices may be to move the pawn, in which case the pawn is no longer protected. Or move the king, in which the pawn is again no longer protected. The player would pass if they could, but it's chess. You can't pass. So the player does one of those two moves and loses the pawn.
Biden is at his strongest running with just himself on the ticket. But he can't run by himself. He has to pick a running mate. And whatever running mate he picks will turn people off. Some people might vote for Biden, however they won't vote for Biden with Abrams on the ticket. And same with Kamala. But he can't pass on picking a running mate. And that's going to make his position weaker.
I like your position, but personally I don't think Biden hesitation to pick a VP is primary to do with making him look weaker. 100% it would, whoever the VP pick is, they'd have to be extremely subdued and hidden behind the curtains. Even the weakest of choices would make Biden look so much worse by having even a modicum of coherency.
The DNC is in a trap. They got one of their lizard people through the primary that, while bought by Communists, isn't really one. He can't make it to the ballot though. He was always mentally inept, but it seems like the campaign trail made him, or revealed him to be, much worse. Well that's fine, we'll just put put whoever we want in and he'll endorse it... except they've had the lazy entitled youth galvanized by Comrade Sanders. Bernie was definitely their worst case scenario(Buttchug had a potential to cost them gravely but not start a movement), they worked hard to keep him out. But those dumb tankies are listening to George W. and can't get fooled again. DNC stacked the deck, and it could of been a lot closer, but it still looks kind of legitimate that they weren't a large enough demographic to lock in a Bernie win. If Biden drops out now, they'll demand Bernie takes his place, and the DNC will be forced to flip them off and go full "Better dead than Red."
So Biden has to make it to the nomination. Corona made that a much more dire thing, pushing back the date as well as Biden being vulnerable. But! If they can make it to the Convention, they can have Biden pick who they want to run, go through the whole pageantry, and before the first Debate, Biden drops out due to health concerns, DNC VP Lizard man steps up having prepared for months to go as hard against Trump as possible for this moment. Then a week or two after that, Biden declares that he is unfit to run, and VP Lizard man steps up to the top of the ticket, having bolstered his reputation with a firebrand denouncing of Trump and being a complete tool for the DNC.
Except, marble brains Joe Biden pledged to pick a female or person of color Vice President. And the DNC has this other problem child, or entitled white Karens who like to inflate their Egos with being the faux saviors of the lesser, poorer races(and I'm including gays and troons as a race). They are just as rabid, much more mainstream than the Commies, and they immediately turned that or into an and. Well shit, now the DNC is run by a council of old white liches than only saw colored folk as decorations to get what they want. A colored man is at least a man, and white woman is at least white, but a colored woman? They now have to scramble to find who they can control that fits the bill and there is no obvious person to fit the bill. All the while this uppity morbidly obese baboon out of Georgia is going through this subset of the party, making a gigantic stink so that she's the only viable option(though the public humiliation they gave her seems to have successfully come with the message to settle down or you're done).
(TL;DR)And that's why I think Biden's VP pick is in such limbo. A) It's not his pick, it's the DNC's chosen presidential candidate. B) She can't be allowed to overshadow Biden before the lock is in. C) It has to come from a pool of people the DNC has likely kept below the threshold of power and control over their power that they want to chose from to give this position to.