The correct answer to this open question is the following.
Although there are no options attached, we can say the following.
What was responsible for the overwhelming majority of the decline in the indigenous populations of Latin America was first, the many diseases that European Spanish people brought when they conquered and colonized the Americas.
Yes, the Native Mesoamerican Indians and Southe American Indians were very clean and healthy people. But they were not immune to the European diseases that almost wipe out 85% of the Native Americans. We are talking about mortal diseases such as cholera, malaria, chickenpox, smallpox, and influenza.
Later, the surviving indigenous tribes were relegated from "modern" society and lacked the proper opportunities to thrive. These indigenous people have lived recluded in their regions or territories, and in many cases do not have basic public services, including good health services.
