"By this point in the 2016 Democratic primary, in contrast, a huge bloc Democratic governors, senators and representatives had chosen a candidate, Hillary Clinton."

Anyway, things were different then. There were "superdelegates," and the elite had reason to think they could control things. Here's a WaPo article from September 2018, "The DNC voted to strip superdelegates of their powers. Will it matter for 2020?":

Ann Althouse  " 'But this cycle, the overwhelming majority of congressional Democrats and Democratic governors are still on the sidelines. Indeed, the 2020 Democratic primary looks more like the 2016 Republican primary, when most GOP officials held their fire until deep into the race, than that year’s Democratic race.... Warren has two obvious problems with party elites. First, there is the perception among some of them that her left-wing stands, such as Medicare for All, are too risky for the general election and decrease the party’s chances of defeating President Trump.... Secondly, electoral considerations aside, there is a center-left wing of the Democratic Party that fundamentally disagrees with Warren’s more leftward positions... Warren also has a third challenge with party elites that is less obvious. The Massachusetts senator clashed with senior aides to President Obama for much of his tenure in the White House. She, like Sanders, isn’t quite in line with the party’s establishment. A Warren administration would probably be less likely to hire former Clinton (Bill and Hillary) and Obama aides in key posts than, say, a Biden, Booker or Harris one. So people connected with the party establishment (like many DNC members) may be fine with Warren but prefer other candidates for more self-interested reasons.... The potential danger for the Massachusetts senator is that 'party elites lukewarm about Warren' turns into 'party elites organize to stop Warren.' And perhaps Democratic voters care more about the views of their party’s elites than Republican voters did in 2016."

"From "Why Aren’t More Democrats Endorsing Warren?" (FiveThirtyEight).

"I wish there were some discussion of the way Democratic Party elites behaved in 2008, endorsing Hillary Clinton early and interfering with the rise of Barack Obama. Aren't they avoiding giving Biden what they gave Hillary in '08?" . . .