On whose behalf did the conquistadors act?

We can say that they acted on behalf of the Spanish crown. At that time, Spain was the most powerful maritime state. Thanks to her funding, the lands of the new mainland were discovered. Naturally Spain sought to be the first to explore these vast and unexplored territories, where it was said to have untold riches. Thus, the Spaniards equipped large military expeditions there, the participants of which were called conquistadors.