@SW-User Well I don't have the emails like in 2016, but let's review what happened.
Sanders was the front runner by being the "runner up" in 2016. The DNC consistently sought to diminish his chances in 2020 by:
Giving undo attention to Warren, who adopted a lot of Sanders' ideas but watered them down to make them more palatable to the corporate entities who fund the DNC.
Constantly pitting him against all the other nominees and forcing him to defend himself from constant attacks.
Favoring/Highlighting all the other also rans like Buttiegieg and Klobuchar and giving them extra attention hoping they would catch on.
Allowing Mike Bloomberg to buy himself into the nominating process. Bloomberg reportedly spent around $500 million of his own money on his ridiculous campaign attempt for the nomination. He only won American Somoa somehow, but did stay in the race long enough through Super Tuesday to drain more votes and delegates from Sanders. I've heard rumors this was the very intention of having Bloomberg run, for had Sanders been elected, his tax burden could have gone significantly up. The rumor is that Bloomberg did the math and it was a better investment for him to run and thwart Sanders from the nomination and possible presidency.
Once Joe Biden won South Carolina, it was very VERY obvious that the DNC went to Buttiegieg and Klobuchar and asked them to drop out and endorse Biden.
Yet at same time, Elizabeth Warren stayed in the race. She hadn't won shit, even after all the money and attention she got. The only reason for her to stay in, while the other 2 dropped out was to siphon votes from Sanders.
For the record, it's pretty clear Sanders does not give a shit. He seems content to be held in regard and have some of his ideas watered down and grudgingly considered. He clearly doesn't care to be President, for if he did, he would not have gone along with this twice now, and still carry water for Biden and the other Democrats.