There were many different reasons why the Spanish were able to take over the Aztec Empire. First, their weapons and armor were better than the Aztecs'. Aztec warriors had only cotton armour and shields made of wood or reeds to protect them. The Spanish had metal armor and shields.
The quality of life starts to diminish. Due to overpopulation, the standard of living of people starts to decrease. It might also bring a negative impact to the economy.