What was a main reason why the Aztecs lost the war against the Spanish?

A main reason the Aztecs lost the war against the Spanish was the combination of superior military technology, such as firearms and steel weapons, and the strategic alliances that Hernán Cortés formed with other indigenous groups who were enemies of the Aztecs. Additionally, the introduction of European diseases, like smallpox, devastated the Aztec population, weakening their ability to resist the Spanish forces.