This was simply a calculated distraction to rile their base away from the fact that Sanders most likely won, and at a minimum, had a very strong showing in Iowa, much better than any “establishment” candidate. The person that “won” is nationally unviable, thus setting the stage for expectations of a brokered convention, which the DNC wants desperately in order to inject a favored establishment candidate.
The subsequent acquittal was a cherry on the top for the DNC, who never really expected to win, and used the whole rhetorical feeling-language-festival to rile their base up even more, hopefully forgetting Iowa.
Sanders supporters are feeling the heat right now, just read /r/SandersForPresident at our favorite site and you can feel the strain, much unlike 2016, where things were much more light hearted.