Why did the Spanish turn to enslaved Africans as a labor force on Americas?

The Spanish turned to enslaved Africans as a labor force in the Americas because indigenous populations were being decimated by diseases brought by Europeans and harsh labor conditions. The African slaves were already immune to some of these diseases and were seen as a more resilient and profitable workforce for the plantations. Additionally, the transatlantic slave trade provided a steady supply of laborers to meet the increasing demand.