Why did the allies help Cortes to defeat the Aztecs?

The Allies, including various indigenous groups like the Tlaxcalans, assisted Hernán Cortés in defeating the Aztecs primarily due to their longstanding grievances against Aztec rule, which was often characterized by heavy tribute demands and brutal military campaigns. These allies saw an opportunity to free themselves from Aztec dominance by collaborating with the Spanish, whom they viewed as potential liberators. Additionally, Cortés's advanced weaponry and horses offered a significant military advantage, further incentivizing these groups to join forces with him against the Aztecs.