None of them would have defeated Trump. After spending more time looking at the results, I am even more convinced that Biden was the only one among major Dem primary candidates who can/did defeat Trump. Major factor behind Biden's win are relatively big gains he made in suburbs and with College Educated Whites. That's what won him PA, GA, WA, MN. Someone like Warren or Sanders or even anyone who is perceived to be left of Biden wouldn't have made the gains Biden made in suburbs or stop the bleeding in rurals.
Could Bloomberg possibly have, maybe? Certainly it would be laughable to try to paint him as a “socialist,” even moreso than Biden, which is why I say he may have had a better chance in Florida. From there he just needs to flip probably one more state — Michigan, Arizona, etc. — and he wins. I do agree Biden was the best choice in the end, and may well have been THE only one (especially because he does seem to have stopped the bleeding in places I’m not sure Bloomberg could have), but if anyone else could have won, maybe Bloomberg? For different reasons if so though. His bigger problem I think would have been lack of charisma and likability compared to Joe.