As the supporters of Bernie Sanders know, he was the victim of a rigged primary with the SUPERdelegates who voted for his opponent, and the DNC chair who organized the primaries against him.
There were many issues that these supporters were motivated about, but two of course were Trade and Wall Street influence.
On Trade, his primary opponent was in favor of NAFTA, and also helped write the TPP. Where she stands on this has been dependent upon the current winds.
On Wall Street influence, his opponent still hasn't released information about her fees as Bernie has requested.
Whether Bernie Sanders has been compromised himself has to be seen. Elizabeth Warren was ignored on many things also.