Why did the king and queen of Spain wanted to convert non believers to Christianity?

The king and queen of Spain, Ferdinand and Isabella, sought to convert non-believers to Christianity primarily to unify their kingdom under a single faith, which they believed would strengthen their political power and social cohesion. The Catholic Monarchs aimed to solidify their rule and diminish religious diversity that could lead to conflict. Additionally, converting non-Christians was seen as a divine mission to spread Christianity, aligning with the broader goals of the Spanish Empire during the Age of Exploration.