Final answer:
The Spanish conquered the Aztecs due to superior military tactics and weaponry, alliances with other indigenous tribes, and the spread of diseases that decimated the Aztec population.
Step-by-step explanation:
The Spanish conquistadors, led by Hernán Cortés, were able to conquer the Aztecs for several reasons. First, the military tactics and weaponry used by the Spanish, including steel armor and steel swords, provided a significant advantage over the Aztec's traditional weapons. Moreover, the Spanish utilized horses for more effective combat. The second key factor was the formation of alliances with indigenous tribes such as the Totonacs and the Tlaxcalans, who were subjugated by the Aztecs and saw the Spanish as liberators. Third, the introduction of diseases like smallpox by the Spanish had devastating effects on the Aztec population, dramatically weakening their ability to resist the conquistadors.
Despite being outnumbered, these factors combined to allow the Spanish to dismantle the Aztec Empire effectively. These advantages, alongside strategic alliances and the impact of European diseases, created the perfect storm that led to the fall of the sophisticated and mighty Aztec civilization.