Why were the Spanish able to defeat the Aztecs?

The Spanish had horses, guns, sWords, and cannon while the Aztecs still used hand weapons and spears. They also had the backing from tribes who disliked the Aztecs, such as the Talaxcala. However the defeat of the Aztecs and the downfall of Tenochtitlan was mainly due to the ravages of disease. Most of the population of the Aztec capital, Tenochtitlan, were wiped out by the diseases the Spanish brought, to which the natives had no immunity.