Most of us believe that life has meaning and purpose. We believe that purpose to be above us as individuals, and that such a purpose is "God" - the causal force for our world existing and what gives it value beyond the material.
Another set of people only see the material. A sort of proto-nihilist who embraces only the tangible. Even then, though, they recognize the value of cooperation that it brings. Even extremely selfish and greedy people will cooperate and behave decently out of regard for the consequences of upsetting the masses.
Then you have the nihilists who can mutate into full fledged narcissists. "Life… Dreams… Hope… Where do they come from, and where do they go? None of that useless junk is enough to fill your hearts! Destruction! That is what makes life worth living!"
The Nihilist has no reason for existing other than what they can rationalize from the apparent chaos and pointless struggle against an inevitable end. The narcissist resolves to the idea that they are god, or the closest thing there can be. In this sense, the war among narcissists is a war among self-proclaimed gods attempting to defeat rival claims and to display their realm's splendor (however that is defined).
Few things demonstrate power like the ability to freely violate taboos. From the social power of having people sacrifice their own moral guidance to glorify your presence to the legal power of being able to commit crimes and not be penalized. It's all an ego trip of the worst order. Anything can be justified as they are a god. We should be thankful they exist to give us purpose beyond our meaningless lives.
There is a method to the madness. It is just dealing with a level of existentialism that most do not deal with.