One sentence from Columbus's journals speaks volumes about his motives. Describing the Native peoples he encountered upon his arrival in the islands known today as the Bahamas, he says; 

It appears to me, that the people are ingenious, and would be good servants and I am of opinion that they would very readily become Christians, as they appear to have no religion. 

Indian peoples, Columbus says, would make ideal servants, laboring to enrich the Spaniards. Yet they would also be willing and easy converts to Christianity. (Columbus did not recognize the religious practices of these people as religion.) Later, encountering another group of local people, he says that he "strove to learn if they had any gold." Columbus was eager to locate gold, which would justify his voyage to his royal patrons, and enrich himself. A personal motive of Columbus is described early in his journals, when he says that the monarchs of Castile and Aragon have 

granted me great favors, and ennobled me that thenceforth I might call myself Don, and be High Admiral of the Sea, and perpetual Viceroy and Governor in all the islands and continents which I might discover and acquire, or which may hereafter he discovered and acquired in the ocean; and that this dignity should be inherited by my eldest son, and thus descend from degree to degree forever.

So Columbus, like many of the Spaniards that followed him, sought to gain status and wealth as well as to win souls for Christianity. These motives, sometimes described as "gold, glory, and God," are made clear throughout his writings, and were evident in his actions. These actions had unspeakably tragic consequences for Native peoples.