Answer:
To introduce one source of the settlers' fears
Step-by-step explanation:
The information about the earlier colony of Sir Walter Raleigh was meant to introduce a factor that must have created doubts and fears in the minds of the new colonists. The settlers sent by Sir Walter Raleigh had disappeared mysteriously.
So, the settlers must have wondered what could have happened to them, and if the circumstances behind their disappearance might have affected them as well. So that was one source of the settlers' fears.