Much of that architecture was from necessity but with a political twist. WW2 devastated eastern European cities and a lot of building had to happen quickly and at low cost. Under communism, though, what we would call western architecture was also considered bourgeois, degenerate, and not at all aligned with the supposedly simple and pure needs of the proletariat. Sameness was a virtue, frivolity and individualism were viewed with great suspicion. The resultant concrete monstrosities were considered a great achievement for the communist regimes for providing housing consistent with the 'values' of the working man.