Seriously, the man has been battling against the establishment, and winning political fights all of his life.
I don't think this is actually true, though.
He's established a constituency in Vermont that consistently re-elects him. That's about the biggest political fight he's won. The high water mark was probably when they elected him to the Senate for the first time.
Other than that? His legislative successes have largely been achieved by
avoiding political fights with the establishment. He adds minor amendments to bills sponsored by other Democrats.
He has not successfully championed any landmark legislation. He has not raised money for the purpose of primarying other incumbents and replacing them with people who share his ideology. He has not been successful at bringing more legislators to his cause, or starting a movement in the nation, beyond the confines of his home state.
There are 25 Blue Dog Democrats, a caucus which started in 1995. But even though Bernie first arrived in Congress four years earlier, there's still only one Berniecrat. He still caucuses with the Democratic establishment he's supposed to be fighting.
His two biggest fights with the Democratic establishment, in 2016 and 2020, have both ended in failure*.
I dunno, maybe in Vermont it's a huge political fight for him to get re-elected every term. But on the national level, he simply doesn't have a history of battling the the establishment and winning political fights. The time he does battle the establishment, he tends to lose.
