Why did the government of Spain support the economic activities depicted in the image?

Under the economic theory of mercantilism, silver was prized as the most valuable of all trade goods.
Silver mined in the Americas was used to fund Spanish conquests of American Indian peoples.
Spain used silver from the Americas to pay West African kingdoms for enslaved people who were used to develop the economies of American colonies.
By using enslaved laborers to extract silver from their colonies in the Americas, the Spanish maintained access to global trading networks with low overhead costs.