While nearing the end of another term teaching courses that explore the intricate dance of religion and society, a perennial thought arose. Christianity is a religion that places proselytizing close to its heart. Early missionaries in different parts of the world debated among themselves whether religion and culture/society must reflect the European integration of these two. That is, was 'correct' Christianity only possible in a European, or European cloned aspect? Was it necessary for missions to convert the society in order to convert to the faith? The Jesuits got into trouble with Head Office in the Vatican sometimes by stretching their frequent, though not uniform, practice of 'going native'. I think of the Jesuits in China who dressed as mandarins and allowed ancestor worship. The Jesuits in Canada seemed to go part way, acting like 17th century anthropologists engaged in participant observation, though at the same time creating separate Christian villages among the Wendat. And of course, there was that early capitalist enterprise, the Hudson's Bay Company that booted Methodist missionaries out of Rupert's land for their habit of attempting to destroy the native hunter-gatherer lifestyle. Not, I add, because of any modern identity politics paradigm but for the hard fact that this damaged the fur trade. In the modern world, there is the Day of the Dead in Mexico; in Africa there are a number of Christian/native religion mixes. I could stretch a point, perhaps to breaking, to mention the official, state-approved 'Catholic' church in China today.
These are just random musings, rather than rigorously researched thoughts on this interesting phenomenon. But I think this gets to the source of the success of Christianity's expansion into many very different cultural contexts around the world. My much more limited understanding of Islam, another proselytizing faith, has encountered the fact that the Sufis - often considered heterodox Muslims by the Islamic mainstream - were the most successful group in converting Africans and Asians to Islam.