What the hell? The Dems pretty much sacrificed control of government in 2012 due to pushing through the health care change. Have a look at their position on climate change and the treaties Obama was signing up to before Trump ripped them up, and compare those positions to Bush/Trump. Obama if anything went too far on being nice for the global alliances. And it was the Dems who passed the automatic rifle restrictions which the Republicans took away.
They may not do as much as some on the left want, but they’re clearly doing heaps on these issues, and the gap between them and the Republicans is HUGE.
He was already an independent senator. The only reason he was even able to run as a Dem was he switched his “team” so he could. In any other democracy in the world he’d have been excluded. And the Dems didn’t rig the primaries, the rules were all there before he even started running.