Holy Light Hunters and the Chairman of the Hunters Association are not the same concept.
The title of Holy Light Hunter represents status, one of the five senior levels of the Dark Hunt Organization, listed alongside the Chief Inspector, the Steward, the Holy Spring High Priest, and the Workshop Chief. Whereas the Chairman of the Hunters Association is a position that represents power, holding control over the Hunters Association and able to deploy Dark Gold and even Shadow Hunters.
Honestly, Casio was not very interested in the Hunters Association, as he already had the vast Secret Martial Arts World to expand his influence. With the Clinic and the Magical Golem Sect, these complementary forces were already sufficient. Too many would only consume massive energy and slow down his Martial Arts progress.
Moderation is key, it's enough to take what is needed.
