Final answer:
Settlers eventually thrived in Jamestown due to the cultivation of tobacco, which became the major cash crop of the colony.
Step-by-step explanation:
The main reason settlers eventually thrived in Jamestown was the cultivation of tobacco, which became the major cash crop of the colony. John Rolfe's introduction of tobacco cultivation proved to be highly profitable and led to the economic success of Jamestown. This success resulted in the development of a plantation system and the encouragement of the slave trade, as an enormous labor force was required to cultivate vast amounts of land for tobacco production.