Final answer:
The Aztecs fell due to Spanish military superiority, strategic alliances with native tribes opposed to Aztec rule, and devastating European diseases like smallpox. La Noche Triste was a temporary setback for Cortés, but with strengthened alliances, he ultimately laid siege to and conquered Tenochtitlán.
Step-by-step explanation:
Reasons Behind the Fall of the Aztec Empire
The Aztec Empire was conquered by Hernán Cortés in 1521 due to a combination of superior Spanish military technology, alliances with hostile native tribes, and diseases that devastated the Aztec population. The Spanish had steel armor, steel swords, and the tactical advantage of horseback combat, which the Mexica, under Moctezuma II, could not match with their traditional weapons. The Tlaxcalans and other tribes that had been previously subjugated by the Aztecs saw the Spanish as liberators and allied with them against their common enemy. The spread of smallpox and other European diseases, to which the Aztecs had no immunity, fatally weakened Aztec society and played a significant role in their defeat. Despite a temporary retreat on La Noche Triste, Cortés regrouped with his allies, laid siege to Tenochtitlán, and eventually captured the city, signaling the fall of the Aztec Empire.