In general, scholars typically say that the men who explored and conquered the New World were motivated by “God, Gold, and Glory.” That is, they were motivated by the desire to convert the “heathens” to Christianity, by the desire to get rich, and by the desire to become famous. We do not know which of these motivations was most powerful in Columbus’s particular case, but we do know that all of them were present to some degree.
Columbus did want to get rich through exploring. He was happy to take the governorship of places that he discovered and he used that power in order to enrich himself. This was very common among explorers of that era. Columbus was also trying to get rich by finding a faster way to get to the spice islands of Asia. Spices were so valuable at that time that a faster route would have been highly profitable.
Columbus did have some religious motives. Scholars disagree as to how much he was really motivated by religion. However, it seems clear that he felt he was carrying out God’s desires when he explored the New World.
Most famously, however, Columbus wanted glory. Specifically, he wanted to be proven correct about his geographical ideas. Columbus was sure that Asia was not really that far from Europe. Many other people believed that Asia was a long way away (going west from Europe) but Columbus believed the world was much smaller. He wanted to sail west and prove that he was correct.
Columbus was motivated by some combination of these three factors in his voyages of exploration.
When I was in school I learned that Columbus travelled mainly to find new spices and to earn money. Spices were worth a lot, so people could make a good amount of money finding and selling spices rather than using Asian spices for profit.
He also went for the credit of finding new land. Several explorers wanted to travel in order to get credit/fame.