There were many forces in the Breezy Plains, and during the battle this time, they had displayed considerable strength. There were six pseudo-Sanctuary powerhouses and many other powerhouses who had power that was at the peak of the Legendary-level.
If it was in the past when those forces were in disunity, Cantory naturally would not take them seriously, because the power of any one force would not be significant enough to cause trouble for the Gilded Kingdom. It was the same case even if a few forces formed an alliance. After all, the Gilded Kingdom and the Illuminati were united, and their combined power was far greater than what a few local forces could fight against.