The vast majority of (Let's use Vietnam as an example) is proletariat. So the vast majority of people are dictating terms to a small subset with different class interests. It's nothing like the dictatorship in, let's say the Netherlands, where a small group of capitalists dictate terms to the large body of proletariat, and the bourgeois political apparatus mediates in favour of bourgeoisie class interests. There's no corruption taking place, just the necessities of market economics.

This dictatorship will naturally "dissolve" when there are no more other classes (bourgeoisie et all) to oppress, since it will no longer serve the proletariat's interests.