Why did Spain decide to back Columbus voyage?

Spain decided to back Columbus's voyage primarily to enhance its wealth and power through new trade routes and territories. Columbus promised to find a westward route to Asia, which was coveted for its spices and riches. Additionally, Spain sought to compete with other European powers, particularly Portugal, in global exploration and colonization. The potential for spreading Christianity to new lands also aligned with Spain's religious motivations during the Reconquista period.