Allen had already planned to ally with the second prince so that their alliance would have the support of the Mage's Association and the military forces of the kingdom.
The only problem left was the support of the majority of the nobles of the Gaia Kingdom. In terms of that support, the first prince surpassed the second prince.
Allen was tempted to mind control the king so that Alisceon and Reid would receive the support of the nobles under the king. But he was well aware that he couldn't do that lest he attracts the attention of Gaia early on.
Since the king was the king of the Gaia Kingdom, it was obvious that he received the support and blessing of Gaia. There was a high chance that the king was well aware of mind magic, so to prevent such a thing from happening, he asked Gaia to give him a blessing regarding that.
