Christians have more resources and funding than most communists organizations, theres an actual interest by the big churches in converting Native Americans, Asians and Africans, which is why languages like Guaraní were preserved and promoted by the Jesuits in places like Paraguay (at sometimes having more speakers than Spanish).
And besides all of that, actual marxist text tends to get ignored in favor of local leftist writers and ideologies like José Carlos Mariátegui, Peronism, Trabalhism, in places like the Global South. Though most of these are heavily inspired by Marx's works, they tend to have some criticism and favor local culture and views over what they see as a Europeanism.