After Isaac heard about the clue that his team found out, he couldn't help but recall Jean's plans to send Vale to the competition, specifically, the Arcane Trial Tower Contest, which was part of the Twelve Academies Competition.
It turns out that the Creation Ring might be one of the rewards to be given to the winner of this contest!
He had agreed to help Jean change the Twelve Academies Competition's requirements for a different reason. It turns out that Jean had deeper plans than him.
He couldn't help but smile at this. He didn't mind that Jean was keeping secrets from him…
He understood fully well that Jean wouldn't be the Headmaster just because of his talent as a Dark Magician. It was because of his cautious behavior, capability to read people, and connections that run deeply.
Without these skills, Jean would not become a Headmaster this early.