Arthur liked to stay in control.
He had sufficient royal rights and ranking status to ensure this control. And the way he had taken countermeasures against Jason's planned or accidental revelation of demonic origins was also commendable.
However, Arthur underestimated Layos' infiltration into the event. It wasn't just participants. Almost half of the moderators sided with the kingdom of Layos. It included sleeper cells, people who were influenced or bought, and lastly, people who were not what they claimed to be-- deep assets.
Arthur's assumptions about the event were based on the premise that the kingdom of Edinburgh was infallible when it came to high-ranking entities. And it was true for the most part. However, the quantity was not everything– especially when it came to the game of double-crossing someone.