I think of Sanders as like a well-meaning version of Trump. He tells people simple, good-sounding things they want to hear. I trust that he truly cares about the working class, but his ideas are probably too big and vague for there to be a path to actually implement them in any Congress of this era. He’s aware of his recent popularity and maybe a little bitter that he hasn’t gotten much out of it. He’s only a Democrat himself to the extent he can gain more from calling himself that than an independent, so with little to lose at this point in his career he’s lashing out while he can win points kicking the Democrats.
Sadly, it only works if you’re selling hate and fear.