Spain’s interests in Latin America after 1520 were largely extractive. That is, they wanted to extract wealth from their colonies in Latin America and send that wealth to Spain.
Spain’s main interests in Latin America revolved around mining. There were other interests that had some importance, but mining was by far the greatest. In what is now Mexico and Peru, Spaniards found massive mines with silver and gold that could be extracted relatively easily. This wealth became the basic reason for having the colonies. Of course, there needed to be all sorts of secondary economic activity to support the miners and the shippers and the government officials, but the economy of the colonies ran largely on the silver and gold that was mined.
So, the main Spanish interests in Latin America after 1520 were centered around mining and sending the minerals to Spain.