Slavery effectively disappeared in most of Christian Europe towards the end of the Middle Ages, because the Church opposed keeping Christian slaves. (Similarly, Islamic Europe had banned Muslim slaves.) As Christianity spread, slaves were no longer conveniently available, and the society had to adapt.

This requires a very bold, 115 font asterisk. Or rather it’s plain wrong. Mass slavery in Europe didn’t really end until serfdom was abolished (1800s). And let’s not even get started on the African slave trade which was managed and prospered off of from Europeans, both from direct sales and indirectly from slave labor. Also, many of those slaves converted to Christianity, so it wasn’t based on any religious affiliation.