When Progressives learn they can't policy wonk their way to the top, they'll start making shyt shake.Pretty much. The goal is to WIN the Presidency first, and then execute your plan. Sanders maybe thought the country was ready for further left ideas, plus while I don't he was racist, his idea of 'All-for-Everyone' sounds a bit tone deaf to a degree... white people are still treated more than minorities, so how could you suddenly convince people was going to get a equal share?
As I said, Bernie is a good guy, with a good heart, but he lacked that understanding you can't preach to everyone with the same message and have the same effect in people's hearts.
In this aspect, Biden probably is one of the best people to watch. Being a politician is just as much as sales as anything else. People have to have confidence in your ideas and confidence in you no matter how shytty those ideas may be.