Why did Emperor Xuanzong of Tang Dynasty abolish Ganyuantang?

Ganyuan Palace is the main hall of Wei Zi Palace in Luoyang Palace in Tang Dynasty. In 656, Tang Gaozong built the Gan Yuan Temple on the basis of the Ganyang Temple in the Sui Dynasty. Gan Yuan Hall is 345 feet wide from east to west, which is equivalent to 10 1.43 meters. Its north-south depth is 176 feet, which is equivalent to 5 1.744 meters. Its height is 120 feet, which is about 35.28 meters. The height of this building is very close to that of the Hall of Supreme Harmony in the Ming and Qing Dynasties, but its width and depth are 1.5 times that of the Hall of Supreme Harmony.