Settlers at jamestown found unexpected success by:

by growing tobacco.

Explanation:

Jamestown was the first British settlement founded on a permanent basis in the American continent on May 14, 1607, in the present American state of Virginia.

The settler John Rolfe introduced a lineage of tobacco, which was successfully exported in 1612, and the financial prospects for the colony soon became very favorable when settlers developed a monoculture of tobacco. Two years later, Rolfe married the young native Pocahontas, daughter of Wahunsenacawh, head of the Powhatan Confederacy, following a period of relative peace between settlers and natives.