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.