It's not that easy.
First of all, communist atheism is fake. It doesn't come from a sincere desire to root out misinformation but from a practical desire to control better
. The state gathers more power by the government becoming a church-like entity and the supreme leader becoming a god-like figure. If religion had been a better way to do it, they'd have probably started a religion.
Secondly, many communist countries were in practice also religious. For the majority of the time during the communist regime, both in the Soviet Union and in the Eastern Bloc religion was only outlawed for the party members (officially, unofficially priests would do religious weddings at midnight as long as you grease the wheels with some cash or foreign luxury goods), the proles had all the church they wanted. But priests would be listened to by assigned informants of the secret police force. As long as you didn't talk against communism or the party or the leader you should be fine tho. And in school they taught atheism in the form of "religion is just man made stories" (I hate commies but go and prove them wrong on this one, I'm waiting).
The Eastern Orthodox church is particularly obnoxious, since it managed to get state backing somehow and crushed under its boot other denominations like Greek-Catholics using political prisons as an "incentive" to force-convert priests. The average man never had any say in it anyway.
So, it's complicated. Americans think in such simplistic black and white terms. It was never simple or clear, in some places communism was just some kind of parasite that latched onto the existing structure, in other places it completely turned everything upside down and built a new society. Anyway, fuck commies.