@bob It is a way social groups try to avoid internal strife, in this case the Democrats don't want to blame themselves both because it avoids uncomfortable soul searching and because it would provide political advantage to Bernie Sanders whom has the hearts of many dissatisfied DNC voters right now, and the establishment wants to keep him out of power.  But by having an external face they can mutually agree upon is to blame, they don't have to risk that internal strife, and can place the blame on something that it doesn't really matter how vehemetly they may fight back against the allegations.