Why did the Maya disappear is a question that has baffled historians for years. Because the Maya disappeared long ago no one will ever know for sure what happened to them.
Many theories exist but none are definitely true.
In the PostClassic period the Maya abandoned many of the cities in the south such as Palenque and Tikal and they migrated northward to settle Uxmal. Then Uxmal was abandoned and Chitchen Itza was settled and ultimately conquered by the people of Mayapan. Mayapan ultimately fell to the Spaniards who tried to convert the people to Christianity and forced many to become slaves. Some of the theories are that over population may have caused people to move because there was not be enough food for everyone. The Maya were a farming people and the farmland would not be fertilized like today.