They didn't distort anything. There was just no other way to build communism.
There wasn't. Because first, they hoped for a socialist revolution worldwide, and then they suddenly realized that their utopia wouldn't work... Lenin, towards the end of his life (he died, I think, in 1924), understood this mistake and wanted not pure communism in the future, but with elements of a market economy (NEP reforms). But Stalin decided that socialism (which, as is known, is the first stage of communism) could be built in a single country (it's as easy as pie...). This is the key mistake, in my opinion. :cool:
And Brezhnev wasn't a saint either.
It's a pity about Brezhnev - there were high hopes for him!