I think each culture had different customs about choosing sacrificial victims. For the Aztecs, they conquered most of their neighbors but left a few unconquere

I think each culture had different customs about choosing sacrificial victims. For the Aztecs, they conquered most of their neighbors but left a few unconquered — these were the city-states they would engage in annual ritual battle where the highest honor was to capture an enemy warrior. When the Spanish invaded, many of these “over-fished” neighbors became eager allies. So the “trade” in that case matured to something kind of ugly, a kind of Hunger Games annual harvest of your best warriors. I can imagine wanting some revenge after decades of enduring that from a hegemonic neighbor.