To make her a goddess was not a particularly difficult feat for him. He had killed many gods and thoroughly dissected them to find out what made them tick and he was sure he would be able to replicate the same process if he wanted to and in a more efficient manner to boot.
The problem was that he had little time to perform this delicate operation and he also did not want to stray far from the Dominion of Trion when he made Circe a goddess, as he needed another backdoor to the Gods of Trion.
This was very important to Rowan, there were certain mysteries about the bloodline of Trion that he could learn if he observed a Dominator as gifted as Circe, it also helped that she was also a Breaker, a moniker that Fury Kuranes styled himself to be.
This was a special bloodline variant created by his father to further his unknown cause inside Trion. If he wanted to begin unraveling the secrets of Trion, he would have to start from here.