Why did Prometheus help IO and encourage her?

Prometheus and Io were in similar situations.... both entrapped. Prometheus by chains, and Io, trapped in a body that wasn't her own. Prometheus told Io to look toward the future. Being that he was chained to the rocks and knew her story, the fact that he still held onto a future served as source of encouragement. In the end, Prometheus was right. Zeus changed Io back into a human and they had a child. Their descendants included Hercules, who would ironically play a large part in Prometheus' freedom.