Why do you think the Europeans killed the Aztecs and Incas?

The Spanish conquistadores were motivated largely by power and when they discovered the riches of the Aztec and Inca empires, they coveted the wealth that would stem from the gold and the natural resources existing on their lands. There was also a great deal of racism at work since the Spaniards believed that the beliefs and customs of the Native Americans were inferior to theirs. However, despite the atrocities committed by the conquistadores, the Aztecs themselves were quite brutal toward their neighbors even before the Spaniards arrived. They were a rather warlike tribe themselves, and indulged in human sacrifice and other customs that people today would regard as barbaric.