Ning Que, who was on the Peach Mountain, was able to find out what the oblation for the Light Sacrifice was. The Tang Empire, which possessed numerous intelligence systems would naturally find out about it, and might have even known about it before Ning Que did. However, Ning Que could only think about how to handle the matter now.
He was basically certain that the news was released intentionally by the West-Hill Divine Palace. The Divine Hall wanted to force the people in the Academy, especially him, out of Chang'an. The Divine Hall thought that he was still in the city and this was a problem they could not resolve. He was so mad at the peak of the Divine Hall of Light because he was certain that the woman inside the hall had chosen Chen Pipi. The Divine Hall of Light sacrifices to Haotian, and since Haotian was in the mortal world now, then only Haotian could decide on its own oblation.