Was it the absence of religion that created issues in communist states? Or perhaps authoritarianism, hero worship, overly centralized planning, low trust culture, or some other combination of factors at play?
History's arc is much longer than communism, and religion is tied to some pretty horrific events.
Given that some of the hatred was targeting specifically religious people (for example, the CCP bans religious people from their ranks), then I think it's safe to say that it is driven by a dislike of religion
You can agree with their take on religion or not, but their motivation remains the same.
History's arc is much longer than communism, and religion is tied to some pretty horrific events.