The fact that you are comparing Bernie to Feingold shows how little you understand about how U.S. politics work. What do Bernie and Feingold have in common? The fact that they're both Jewish?
Feingold lost because he has been out of politics for awhile and not particularly active on major issues, and people felt he wasn't in touch with Wisconsin issues anymore. Does he even live there?
Almost every single line of this post is wrong. My guess is you just started paying attention to politics a few years ago to support Corbyn and Bernie? The similarities between Feingold and Bernie are obvious. Feingold was the hero of many Bernie supporters back when Bernie was still a backbencher in the House and nobody outside Vermont knew or cared who he was.