What do we know today about the decline of the Mayan civilization around 900 A.D.?
1) Historians do not know exactly why the Mayas abandoned their cities.
2) Crop failures brought widespread famine to the Mayas.
3) The Mayan peoples rebelled against their leader, Moctezuma.
4) Costly wars with the Aztecs forced the Mayas to move to Tenochtitlan.