The DNC completely restructured their convention process after this happened. Sanders and his supporters fought hard for this change, at least try to pay attention:

Adoption of superdelegate reform (2018)

On August 25, 2018, the DNC approved a plan to reduce the influence of superdelegates by barring them from voting on the first ballot at the Democratic National Convention, allowing them to vote only in a contested convention (i.e., if a Democratic National Convention did not choose the nominee on the first ballot, because no candidate received an absolute majority (more than 50%) of the pledged delegates elected from the outcome of primaries and caucuses). This does not preclude superdelegates from publicly endorsing a candidate of their choosing before the convention.