I think it's quite possible the level of violence seemed excessive even to the society itself. A common problem that's cropped up in a number of modern countri

I think it's quite possible the level of violence seemed excessive even to the society itself. A common problem that's cropped up in a number of modern countries is weddings getting more and more expensive. If weddings are an important means of displaying status, and it might shame the family to seem poor, then there is clearly going to be a drive that direction. Pretty soon, people are bankrupting themselves on weddings that seem excessive to everyone involved. Cultures that engage in religious sacrifice seem to have the same sort of problem. Sacrifice shows off both status and religious zeal, so there's incentive to try to sacrifice more than others. If sacrificing slaves is allowed, ending up in an extreme state isn't all that surprising.