How did the Aztec culture perish?

Spanish conquistadors commanded by Hernando Cortez arrived in the same year that the Aztecs believed their god Quetzalcoatl would return. At first the Aztecs believed that Cortez was Quetzalcoatl, but Quetzalcoatl was a bloodthirsty god who demanded human sacrifice, and the Spanish were disgusted by this practice. Cortez' army was small but much better equipped, and they found thousands of allies in subject tribes which the Aztecs had conquered and were using to feed Quetzalcoatl. The Aztec king, Montezuma, was killed by his own people when he tried to prevent war with the Spanish, and and the Aztecs were defeated eventually. The Spanish also brought missionaries to Mexico, and the religion of the Aztecs was quickly replaced by Roman Catholicism.