Could The Bern be in it to pocket the remains of his campaign $$$?
Is he in it to keep/pocket the remains of the campaign funds he's raised?
Seems to me The Bern must be 'in on' the D's party primary CON of rigging the race via their super-delegate rules.
He knows he serves a purpose– shifting the Overton Window (https://www.mackinac.org/OvertonWindow) toward the Radical Left, thus making Biden 'appear' more moderate, when Biden's clearly not moderate at all. Crazy Bernie also gets to retain what's left of the campaign funds he's raised I believe:
""If Biden walks into the convention, or at the end of the process, [and] has more votes than me, he's the winner," said Sanders, before confirming he would concede whether the lead was a majority or a plurality… "I think it would be a real, real disaster for the Democratic party," said Sanders. "People would say 'the person who won the most votes didn't get selected.' Not a good idea."
https://www.newsweek.com/bernie-sanders-will-drop-out-if-biden-gets-plurality-coming-dem-convention-1490614