Christopher Columbus believed, like many other explorers, that there were riches waiting to be found in the New World. Columbus was a sailor and trader who had done business around the Mediterranean and along the Gold Coast-- with rumors that a trade route could be established in the Atlantic Ocean, naturally he saw it as a business opportunity. European demand for spices, gold, and other luxury items was rising with a sense of panic as the Ottoman Empire closed around them, cutting off trade routes to the South and East. As competitive spirits between Spain and Portugal (two major colonist-trade nations) were rising, Columbus felt that it was in his best interest, and the best interest of Spain, to take a leap towards what most people believed to be the edge of the world.
Though Columbus expected to sail directly to the Eastern edge of Asia, he found the Americas in his way. No matter! This provided him the opportunity to evangelize the locals he encountered. He both "claimed" land in the Americas for Spain and initiated the process of Christian imperialism in the New World.
Columbus' goals and motivations were entirely the product of the economic, political, and religious context he had grown up in. All of Europe were in high competition with one another to become the wealthiest and most expansive nations (or empires) while facing the threat of the Ottomans closing them off from their sources of wealth. Columbus believed that it was his duty to evangelize non-Christians, and his God-given right to claim land and profitable resources for the Spanish monarchs. These were his goals.