Matthew Yglesias for Vox:

The problem: Sanders had little control over his delegates, who seemed unwilling to get behind his endorsement of Clinton. This was in part a matter of sloppiness on the part of Sanders’s team in selecting delegates. But as one operative told me, there was another reason Sanders’s delegation was so unruly: Everyone was so afraid to cross Clinton by serving as a Sanders delegate that he couldn’t convince the kind of party loyalists who normally take the job to do it.

Instead, many Sanders delegates come from the world of left-wing protest culture rather than party politics. And on the floor of the Wells Fargo Center, they acted like it.