By showing Superdelegates in the delegate horse race, they were used by the media to show that Bernie had no chance, so they gave credence to the people who said he couldn't win. And a lot of people voted for Clinton in the primary because they didn't think Bernie could win.

Basically, when the leading candidates are all acceptable to the establishment and their oligarch masters, the superdelegates don't really matter. They've always gone along with the popular vote. 2016 was different. One of the leading candidates was unacceptable, so the superdelegates were used as they were intended: to prevent the party leaders from having to campaign against a grassroots candidate. That's what Debbie Wasserman Shultz herself said they were for.

Had Bernie won the regular delegates by even a couple hundred, he still would have lost the nomination. A populist candidate must win by a margin larger than the number of superdelegates. 2016 showed that it's pointless for someone outside the ruling class to run as a Democrat.