Why were the Aztecs defeated?

Answer 1

the Aztecs as other native American races were defeated for several reasons:

the spanish soldiers had allied with other tribes to defeat them (the tlaxcalls)

the spanish soldiers carried diseases that killed many Indians (smallpox)

the spanish had technologies that gave them advantage in combat (horses powder and different combat strategies)

Answer 2

The Aztecs were defeated because two tribes teamed up and stopped food and water getting to the Aztec, then when the Aztecs were weak the spanish and the other tribe attacked.