When news about the abdication of King Regan covered all the surrounding kingdoms of Qalagon, the coronation ceremony for Crown Prince Arin as the King of Qalagon was already done.
The retired King was well aware of how their enemies saw his successor as a threat to them. As such, all the preparations were done cautiously not to let the enemies get a grasp of the news. So, when the enemies finally heard it, everything was already done.
Arin Helev was already quite a force to reckon with while he was just the Crown Prince. So, the enemies knew that he will only become more formidable once he became the King. They were always wary about that and now... it happened all of a sudden, taking everyone by surprise.
Though the officials were quite against it when the abdication was first mentioned, they eventually gave in to the King's wish. After all, the successor wasn't the reason why they were against it. No one doubt that the Crown Prince will make a great King.