Marx’s view of communism doesn’t inherently ban religion. His view of religion was that it was a tool by the ruling classes to maintain the status quo against the oppressed, and that under communism religion wouldn’t hold any political power because, by his words, the conditions that allowed religion to hold political power such as inequality wouldn’t be present anymore. But he didn’t call for the abolition of religion or that religion couldn’t exist at all in a communist society, that was more of a Marxist-Leninist way of thinking.