The Yemassee were worn out from their relationship with South Carolina as they felt the white settlers were cheating them continuously.
Explanation
At the latter half of the 17th century, there was a cooperation between the tribe of Yemassee and settlers of South Carolina.
But these all were changed when Yemassee tribe realized that they were being manipulated in many deals and trades with the white settlers turn out to be abusing.
The white settlers pressured them on the subject of agricultural lands and hunting.
Also, the tribes were dependent on the settlers for trades where many discrepancies occurred.