The archaeologists need to know about the rain patters in the period and place where the Maya existed because the rain was crucial about the growth and well being of the crops that this civilization used. A longer drought than usual can make a huge problem with starvation, and that can be a key reason for the fall of one of the greatest civilizations in the Americas.
''The Maya world probably had too many people'' refers to the food supplies available and their reserves, and the amount of people that were using them, so it is thought that the Maya had too many people that produced and used limited amount of food, so their reserves were very low and would have lasted for a very short term period of time.
