Why is the Democratic Party against the only person who could save them?

[Mister Agenda]

Bernie is the single most effective politician in Senate or Congress. Why is he treated like gatbage?! Additionally why is the Democratic Party so goddamned thick, they'll throw away provressives like during the election, and opt for a quid pro quo with republicans where they wI'll always be perpetual losers,  in exchange for a little piece of the pie??? Get money out of politics and everyone will be on equal footing! 

https://youtu.be/ZmPsX2tNV1Y

For one thing, he's not a Democrat. He was an independent before his presidential campaign, became a Democrat for purposes of running a campaign with a chance of winning, and returned to being an independent when it was over. From the point of view of Democrats who worked in the party for decades, the only thing he accomplished last year was to get Trump elected. I don't see why their point of view would be so mysterious.