The Establishment is not “the set of people who have power”, and it is not “the set of people who hoard advantage for personal gain”. In fact, those sets are often disjoint, or even adversaries.
The Establishment is the framework of institutions, customs and rules that have been found to serve both groups, without the two having to collude directly. It’s elite schools, highbrow fundraisers, political parties, propaganda newspapers – any vehicle that justifies greed politically and justifies power economically.
Prior-restraint censorship is a perfect example of such a vehicle. It serves rentiers because it’s far easier to extract rent on information after it’s published; and it serves the authorities because they can exercise power outside of public scrutiny; and neither group has to acknowledge the other’s interest (which would be “corrupt”).
The fact that it’s objectively wrong is notable by its absence from the discussion. When something is separately desired by both the rich and the powerful, you get to see just how little the interests of the majority of people really matter.