Raydon had previously noticed a significant expansion in both the potency of his aura and the range it encompassed when he utilized the aura technique, thanks to the sub-skill he obtained upon raising his spirit stat to 100.
And then, with Zpehyr's explanation, when he realized that it was actually a domain, he believed that the spirit sub-skill was having an effect on his domain. However, up until this point, he had not attempted to test it using the aura sub-skill that is associated with his stamina stat.
In spite of the fact that these aura sub-skills operated in the same way as passive skills, they were, in fact, semi-active skills that did not become active until Raydon selected a target. Now that he had gained this awareness, he made the decision to attempt to combine his aura technique with the aura sub-skill of the charisma stat that he had just recently acquired.