Also, endorsements of candidate B from elected officials of the Dem party means an automatic "superdelegate" vote for B in the primary election - a fact which, when considering the proportion of superdelegates, heavily weighs the result. So the primary isn't purely democratic, superdelegates having at least the theoretical ability to, en masse, supersede a clear majority of primary voters.

This obviously weighs in favor of big moneyed candidates representing the establishment, the status quo.