This servant, who is not named, but may have been Eliezer (See Genesis 15:2) probably had heard Abraham praying. Perhaps he had participated in household prayers with Abraham and other servants. God answered his prayer immediately, as Rebekah came to the well, and acted as the servant had prayed. The fulfillment is a miracle. Why should a young woman strain herself to water the camels (That must have been a lot of water!) of a man she did not know? And, of course, there was the greater miracle -- she agreed, readily, to leave her family, her friends, her familiar surroundings, and probably her religion, to travel across the desert to marry a man she had never seen. God answered that prayer mightily.
Was Isaac praying for a wife, back at home? Was Abraham praying for a successful mission for his servant? Had Rebekah been praying for a husband? We don't know.
Years ago, I sometimes prayed that the God, who found a wife for Isaac, would provide me with one. He has, and I am grateful.
Thanks for reading.