Because as much as everybody on hexbear likes to shit on Bernie and pretend he's literally as bad as the rest of the democrats there was a very real effort to have anybody but Bernie win the primary, and Biden just happened to luck out into being the one the rest of the shitlibs coalesced behind
it always seemed like The Democrats wanted Kamala Harris or Buttigieg, though, and especially making her VP despite her being the First Place Loser of the Primary (not even winning her own state) made it seem like that was The Plan, have Biden win the election and then mumble some stuff about health issues before handing it off to The Anointed One
I didn't expect Biden (or his handlers, depending on how dementia addled he actually was) to give a shit about him personally being President