Central Mexico was very fertile farm land back then and could have supported a large population. A lake once existed where Mexico City is today, and many Indian kingdoms existed along its edges and irrigated from it. They even had floating gardens on the lake. They were a smart and sophisticated people, yet, they let the barbarity of the Aztecs overwhelm them. Then came Cortes!
***and many Indian kingdoms existed along its edges and irrigated from it.**
They could not have. The lake was salt water.