Spain had a lot to gain by supporting Columbus and his explorations. Spain, France, and Britain were rivals. The Spanish were looking to spread their influence and way of life around the world. By supporting Columbus, Spain was hoping several things would happen.
Spain wanted to control more land. Spain was hoping Columbus would discover new lands, claim those lands for Spain, and report back to the Spanish leaders about what he found. This could lead to future explorations and controlling more land. This could also increase Spain’s power and give them an edge over their rivals.
The Spanish also hoped that Columbus would find new trade routes or lots of minerals. New trade routes would lead to more profit for Spanish merchants. Discovering minerals such as gold and silver would add riches to the Spanish treasury. This would allow for more explorations that could lead to more power for Spain. It also could allow the Spanish kings to continue to live a luxurious lifestyle. Spain had every reason to want to support explorers and their explorations.