During Wu Zetian's reign, he tried his best to crowd out the dissidents in the court, so the situation at that time was that whoever did not stand on Wu Zetian's side would be unlucky. However, there was a man who supported Tang Gaozong before his death. He also said that this man was not the enemy of Wu Zetian. But after his death, Wu Zetian saw a dress in front of his grave, which made Wu Zetian thoroughly see through the man's intentions and called him a cunning man. This man is Xu Maogong.
Facts have also proved Xu Maogong's prediction that when Wu Zetian proclaimed himself emperor, Xu Jingye wanted to use the situation to provoke the descendants of Li Shimin to revolt, in the name of Luling Wang Li. As a result, the army was defeated and killed, and the Xu family was also slain.
There is a famous figure named Xu Maogong in The Romance of Sui and Tang Dynasties, who is resourceful. Later, he was one of the founding heroes of the Tang Dynasty. Xu Maogong, the founding hero of the Tang Dynasty, was poached by Wu Zetian because of his grandson Xu Jingye's complicity. Wu Zetian dug Xu Maogong's grave to discredit Xu Maogong. She thinks that there must be a lot of gold, silver and jewels in Xu Maogong's grave, and it is possible to find some evidence of Xu Maogong's rebellion when he was alive. Wu Zetian was disappointed. Xu Maogong is an upright official. In his tomb, only a set of official uniforms was found, and nothing else was found. This is also the failure of Wu Zetian when he was in power.
When Xu Maogong was alive, he said that his grandson was too courageous and was afraid of big trouble in the future. Wu Zetian dug Xu Maogong's grave, not only to vent her anger, but also for political purposes. After all, everyone knows that Xu Maogong is the hero of the Tang Dynasty, and his grandson rebelled, so he should not be implicated. But Wu Zetian's method is brilliant, even punishing people. He thinks that Xu Maogong's grandson made a mistake and Xu Maogong is not worthy of respect.
The above is my understanding of this history.