You can’t see why humans who worship their god of death might include genetically similar people who don’t worship their god of death in their mass human sacrifice rituals? Especially if doing so allows the death-god-worshippers to assume to status of “most oppressed people on earth, whom you may not question the actions of in any manner whatsoever” (while they continue to spread endless death, destruction, and suffering)?

Well, good luck with that. Try to chew on it for a while.