The primary reasons for Spanish settlement in the Caribbean were wealth and power. When Columbus first landed in the “New World,” he was seeking a trade route to India. He never found that, of course, but he did happen upon a grand opportunity for Spain to expand its network of trade and to develop an empire.
Early Spanish explorers were always on the lookout for gold, and they found just enough to make them want more. So they expanded their explorations and started colonies as bases of operations for their search. They found more of what they were looking for, a lot more, in Mexico and South America, and their conquests and colonies expanded further with the Caribbean serving as a shipping base.
The Spanish also found a different kind of “gold” in the Caribbean—namely, the expansion of cash crops like sugarcane, which could be sold in Europe for large amounts of money. Settlers established plantations, enslaved the Native Americans to work on them, and began accumulating more and more wealth.
As they searched for gold and grew crops, the Spanish also expanded their rule over more and more of the Caribbean and the Americas. They claimed many territories for their native land and expanded the Spanish empire far and wide. Spain's rulers were pleased with their growing influence in the world and the power it gave them in their competition with other nations.