You’re forgetting that the Nazis utterly ane completely destroyed the USSR, digesting an entire generation of men in every soviet state along with all of their infrastructure and resources.

In the end it was the sacrifice USSR which enabled USA and UK (lots of Uniteds here) to claim victory. As a thank you, the west invested considerable resources into rebuilding Germany and Japan while giving the USSR and China the middle finger and immediately treating them like enemies.

We really did kick Russia and China while they were down, repeatedly, then spit on them.

It did however need to protect itself from the constant threat of annihilation by the US. At one point US generals were proposing to preemptively nuke all of the USSR because their own losses would be acceptable.

So it didn’t help that a developing economy had to redirect a sizeable portion of its productive power towards defence. Nor did the constant less direct attacks from the US and its allies. Despite all of that, average workers had good conditions even when compared to the US itself.