It baffles me as well. There’s a section in 1984 where Winston tries talking to an old man to ask him whether the old system under the capitalists was as bad as the propaganda makes out. The story also mentions that the socialists took power.

From 1984:

“Collectively, the Party owns everything in Oceania, because it controls everything, and disposes of the products as it thinks fit. In the years following the Revolution it was able to step into this commanding position almost unopposed, because the whole process was represented as an act of collectivization. It had always been assumed that if the capitalist class were expropriated, Socialism must follow; and unquestionably the capitalists had been expropriated. Factories, mines, land, houses, transport—everything had been taken away from them; and since these things were no longer private property, it followed that they must be public property. Ingsoc, which grew out of the earlier Socialist movement and inherited its phraseology, has in fact carried out the main item in the Socialist programme; with the result, foreseen and intended beforehand, that economic inequality has been made permanent.”