I've not said anything that even borders on conspiracy theory. It seems like you just throw that label at anything you don't, or don't want to, understand.

Former Presidents typically have tremendous influence in their parties. Biden went from near the back of the pack to a clear first place on one super Tuesday due in large part to Obama's influence. Every establishment friendly candidate dropped out on the same day and endorsed Biden due to deals made or brokered by Obama. Likewise, in 2016, Hillary had the machinery of the DNC behind her candidacy long before the primary even began. Leadership in the DNC, DCCC, and a myriad of other organizations that collectively make up the Democratic party is chosen largely through back room deals and endorsements. Then there are the lobiests, Democratic consultants, and wealthy interests who all benefit from their relationships with former presidents. Soft power may be difficult to nail down, but is undeniably a huge driver of Democratic leadership.