I never did get how this part of Bernie’s base when it comes to “impeachment is a neoliberal scam to avoid the issues” squares the peg that Bernie doesn’t support that notion in any way
Populism is the answer. There's a ton of people on the far right who simultaneously want things like kicking out all non-whites, and simultaneously supporting reduced education and healthcare costs (for whites at least) and isolationism, and support Bernie because he wants to do the latter and feel he'll also do the former, who then voted for Trump because of the former. It's certainly a strange mix but also explains why there's such an overlap among some Bernie and Trump voters.
