Drought: Chichen Itza relied heavily on rainfall for agriculture, and a prolonged drought in the 12th century may have caused widespread crop failures and famine, leading to the collapse of the city.
Warfare: Chichen Itza was constantly at war with its neighbors, and the city may have been weakened by a series of defeats in battle.
Internal Strife: Chichen Itza was a highly stratified society, and there may have been internal conflict between the ruling class and the common people.
Epidemic: A disease outbreak could also have decimated the population of Chichen Itza, causing the city to collapse.
Natural Disaster: A hurricane, earthquake, or other natural disaster could have destroyed Chichen Itza, forcing the inhabitants to abandon the city.
It is likely that a combination of these factors contributed to the fall of Chichen Itza.