This is because Wu Daozi had an unsurpassed reputation in the art world and at home before his death, and even those in power at that time greatly praised him, so he had such a high status and reputation.
firstly, Wu Daozi just didn't have the original works handed down, but he kept some ornamental paintings. Wu Daozi was born in a poor family, and then he drifted around and had no fixed place. However, at that time, it was the unprecedented prosperity of the Tang Dynasty, the advanced economic strength and the development of various cultural rituals and rhymes. Therefore, Wu Daozi had been to the temple at that time and left his paintings on the walls of the temple. Moreover, these works are vivid and lifelike, and they are all famous and excellent in the local area. His teacher also appreciated his talent very much, and even recommended him to many cultural masters, who taught and influenced him. Finally, his painting technique and artistic conception are far-reaching, wonderful and amazing.
Secondly, as Wu Daozi's painting reputation was praised by more and more people, he was finally introduced to the palace by the authorities and became an excellent court painter. His experience also made him better known and praised by later generations. After Wu Daozi entered the palace, he had sufficient resources to complete his paintings. He once created a picture of the Five Dragons, which was very amazing. Every time it was rainy, lightning and thunder thundered, and his paintings seemed to be alive, hovering and waiting.
Later, Wu Daozi was sent by Xuanzong to create a river map, and then he lived up to expectations. In just one day, he finished a beautiful landscape painting, and his techniques became the object of study for future generations. Another painting was when Xuanzong was ill. At that time, Xuanzong had a nightmare, dreaming of Zhong Kui, a ghost and ghost catcher. Worried that it was a bad sign, he ordered Wu Daozi to create a portrait of Zhong Kui. Although Wu Daozi didn't know what Zhong Kui looked like in Xuanzong's dream, he was exactly the same as the person in his dream after the creation, which is also the reason why every household posted a portrait of Zhong Kui later.
To sum up, this is why Wu Daozi's original works have not been preserved by future generations, but they still enjoy a high reputation.