I think that the theory that was mostly to be true was disease. I think it was very plausible that a disease from some sort of bug, animal, or plant could have spread.
The Mayans lived in Central America in Mexico.
There are 4 main theories for the disappearance of the Mayans. The first is warfare. Some people think that they died off from war. The second theory is that they died from disease. It was easy for disease to spread during that time. The third theory was that they ran out of food. And the last big theory was a disaster or environmental change. Back then they were not prepared for some natural disasters.
The Mayans had a sophisticated a complex calendar. The calendar uses 3 different dating systems: the Tzolkin (divine calendar), the Haab (civil calendar) and the Long Count. Tzolkin combines a cycle of 20 named days with another cycle of 13 numbers, to produce 260 day count. The Haab was the solar calendar with 365 days. The Long Count was a non-repeating calendar.
The Mayans were highly skilled architects who created structures with great precision.El Castillo or the Pyramid of Kukulkan at Chichen Itza is one of the most famous Maya structures. Its 365 steps equal the number of days in their solar calender.
They were great astronomers. The Maya made meticulous observations of celestial bodies, recording astronomical data on the movements of the sun, moon, Venus, and the stars.