You did not explain how the “ruling class” was not the majority of society. You explained that you have an incomplete, non-Marxist view of what class is, and thus we are talking about entirely different subjects.

Classes are relations to ownership of production, not levels of wealth, and not hierarchy. The ruling class of the USSR was the proletariat, administrators were proletarian and the state was run in the interests of the proletariat. Capitalists, fascists, landlords, kulaks, etc. were the oppressed classes and had their property expropriated.

Ruling class does not mean leadership, nor “tiny,” it refers to the class in power.