You ought to recognize that Bernie comes from a pretty different primordial soup than any other major US politician. While he's quite similar to Hillary in practice, his priorities are somewhat different. As an example, he wouldn't be satisfied with universal health care if it happens on the terms of profit-seeking companies. He's a big opponent of campaign finance reform, Wall Street speculation, and international capitalism because he believes the wealthy have too much power, and this power should be curbed. While Hillary Clinton discusses the wealth divide occasionally, she's really just advocating for the standard Democratic platform. Bernie Sanders and the Democratic party have never seen eye-to-eye, and the Democratic party has a pretty checkered history of fucking over other leftist groups. Had the Democrats' tolerated his viewpoints during the days of Mr. Clinton, Bernie Sanders would have become a registered Democrat much earlier than 2015.