That's the most plausible theory, but why not promote a candidate that's actually liked by the far left? They're only settling for Biden. Why not put up some populist leftist like Bernie or Yang? They won't win but they'll bring a big turnout, and the DNC doesn't care about those candidates anyway so no problem wasting them. Instead they bring out a repeat failed presidential candidate who was an idiot before he had dementia, and the woman rated lowest in the debates.