I think the Maya Civilization ended because of all the theories (warfare, over-population, over-demanding rulers, and climate change.) Since no one knows for sure, it could be the combination of all. I think they left because of all these reasons because all those factors could have happened at the same time. Warfare was probably a factor because people were scared to stay in their cities, or they couldn't provide for themselves. Over-population was probably a factor because the cities got too crowded, and people thought there was more to the world. You get the idea. So this is why I think these are the reasons to the decline of Mayan Civilizaton.