Secondly, it seems faintly absurd to blame Obama when Biden had to win a full Democratic primary and election campaign. He had to do this on his own merits. Being VP certainly would have increased his brand recognition, but he was an ambitious man (he'd run for president twice before), had a strong political background as senator and fit the party's desire for the most boringly moderate, common-talking, straight, white man they could find.
No, that one's actually on Obama. He personally organized the mass "dropout and endorse Biden" wave over the 48 hours following 2020's South Carolina primary -- which Biden didn't even win thanks to "the black vote", he won thanks to a massive surge in suburban, white, conservative primary voters. Prior to that, Biden was in the process of actively crashing out, managing to overcome the phenomenon of name recognition among low-infos, largely thanks to (credit where it's due) Harris dogging him in debates and media over racial issues in her own bid to be the "anyone but Bernie" chosen. That set the stage for Super Tuesday, after which the primaries were effectively over.
It just happened to be the case Biden was the only candidate in the Democratic field polling better than syphilis, and had managed to put points on the board sufficient to justifiably challenge Bernie. Especially after that shitshow in Iowa, replete with its numerous instances of state-level Democratic officials getting caught red-handed openly cheating to swing delegates Buttigieg's way.
2020 is, if anything, an active example of what happens when Biden has to do things "on his own merits". Just like 2008 when he crashed out over those stupid racist-ass comments made about Obama, and in 1988 when he crashed out over plagiarism and lying about his college record. And even with the astroturf support of the entire Democratic party, in the middle of a global pandemic and on the precipice of an economic crisis to rival the Great Depression, he only
barely beat the likes of Donald Trump.
I mean hell, Obama himself was the one to say "don't underestimate Joe [Biden]'s ability to fuck things up".