Why did Columbus's voyage to the New World mark the beginning of a conquest rather than a discovery?

While it's partially true that Columbus's voyage led to a "discovery" of the New World, his trip more accurately lead to a conquest. Upon figuring out that the place Columbus had sailed to was a "new world", filled with gold, silver, and treasures of all sorts, the Europeans decided to venture this land and "claim it". Examples of conquests would be the Spanish conquest of South America: the conquistadors. Francisco Pizarro invaded and conquered the Incan Empire in the Andes region and Hernando Cortez had done with the Aztec Empire in central America.