Answer:
One important factor that contributed to Europeans being able to conquer the Aztec and Inca peoples was their possession of far superior weapons and military technology.
The Aztecs and Incas, while advanced civilizations in their own right, were still fighting with weapons like clubs, spears and archaic armor when the Spanish conquistadors arrived. The Europeans, on the other hand, had guns, cannons and steel swords - weapons and armor made from superior materials.
When the Spanish conquistadors, along with their horses, guns and cannons first confronted the Aztecs and Incas, the native populations had never seen anything like it. The advanced European weaponry and military equipment gave the conquistadors a huge tactical advantage that the Aztecs and Incas could not match.
The Aztecs and Incas were also unfamiliar with and undisciplined against the tactics of cavalry and artillery that the Spanish employed. This, combined with the psychological impact of seemingly magical weapons like guns that could kill at a distance, contributed to the Spanish being able to conquer the Aztec and Inca civilizations relatively quickly despite being vastly outnumbered.
So in summary, the technological and military gap between the relatively primitive weapons of the Aztecs and Incas and the far advanced weaponry of the European conquistadors was an important factor that helped enable the Spanish conquest by giving them a decisive edge on the battlefield.