Why did american indian tribes cortes to conquer the aztec empire?

The American Indian Tribes helped Cortes to conquer the Aztec Empire because they will benefit from its downfall.

The Aztec Empire practiced human sacrifice. They sacrificed 10,000 to 50,000 humans a year. These human sacrifices were either war captives or those kidnapped from neighboring communities. A lot of people fear this practice, thus, they assisted Cortes in conquering the Aztec Empire to put a stop to human sacrifice.   

Dpolitical is the answer