There are archeological theories which suggests that one of the reasons the Aztecs and the Maya disappeared is because they sacrificed, killed in battle, and actually ate each other to extinction. By the time the Spanish arrived, the indigenous peoples were already weakened and in decline.
Since they had no concept of modern 'conservation' they were depleting their natural environment with no thought of the future. The Sun God provides for all no matter what. So when they began to run out of resources, the sun Gods were angry. And the obvious religious solution was to sacrifice a few more thousand people. When God is happy, everything will be good forever.
