Why were the spanish able to easily conquer the aztec and inca?

The Spanish explorer Francisco Pizarro invaded the Incan Empire in 1532, seeking riches. The Inca had already had some contact with Europeans, and many had died of European diseases. The empire was also weakened by a civil war between two ruling brothers. Pizarro manipulated the two sides, eventually defeating both.

Because when the Spanish came to the Americas they brought diseases with them. These diseases killed large numbers of Native Americans. These diseases also killed off the Natives food sources. The Spanish also had fire power which allowed them do dominate the battles they fought. Where the Native Americans had wooden spears, bows, arrows, etc. They used stone as aow heeds. Thaiss allowed the Spanish to easily conquer the Aztecs and the Incans.  
  hope this helps :)