Francisco Pizarro wasn't the first Spaniard to overthrow a South American civilization. When Hernan Cortés came to Mesoamerica with his galleons and guns, he subdued the Aztec people with few men. In general, he denied offers of peace and coexistence in favor of plunder and enslavement.
Cortés sailed to South America from Cuba under the Spanish flag, but against the protests of the governor of Cuba, Diego Velázquez, who wanted to put someone else in charge of the expedition. Back home in Spain, Velázquez painted Cortés as power-hungry and reckless. But King Charles V forgave Cortés after he conquered the Aztecs in 1521 and returned home with their wealth.
Despite the murders and deaths of tens or even hundreds of thousands of Aztecs, the explorer inspired others to follow in his footsteps. Not the least of these was Francisco Pizarro. He, too, wished for riches, and he followed Cortés' example.