Spanish settlements in florida were at the heart of this reason for settlement

Spanish Florida (Spanish: La Florida) was the first major European land claim and attempted settlement in North America during the European Age of Discovery. La Florida formed part of the Captaincy General of Cuba, the Viceroyalty of New Spain, and the Spanish Empire during Spanish colonization of the Americas. While its boundaries were never clearly or formally defined, the territory was much larger than the present-day state of Florida, extending over much of what is now the southeastern United States, including all of present-day Florida plus portions of Georgia,[1] Alabama, Mississippi, North Carolina (see Fort San Juan), South Carolina,[2] and southeastern Louisiana. Spain's claim to this vast area was based on several wide-ranging expeditions mounted during the 16th century. A number of missions, settlements, and small forts existed in the 16th and to a lesser extent in the 17th century; eventually they were abandoned due to pressure from the expanding English and French colonial projects, the collapse of the native populations, and the general difficulty in becoming agriculturally or economically self-sufficient (which also affected some early English colonies). By the 18th century, Spain's control over La Florida did not extend much beyond its forts, all located in present-day Florida: near St. Augustine, St. Marks, and Pensacola.

Explanation:

they died because of a disease during the first spanish colonies.