A costly mistake
The universe that Immortui was in wasn't currently as large as the one where Earth resided, nonetheless it was still a universe, so the space would seem infinite to most and if one tried to attempt to travel and visit every area possible, it would be a next to an impossible task.
Not unless one had special abilities or use of a certain type of travel that the gods tended to use. Nevertheless,the battle between the great demon king and Quinn had sent shockwaves through the universe. The particles of energy in the air were sharing the vibrations of power on and on, making the one and only Immortui aware of what was going on.
Not only that, but the region where the great fight was taking place, Immortui had quite a few close to the area, since that was where the champions resided. Although two of them were willingly working for Immortui, he never felt they were loyal like that of the demon kings.