You should know how much Wu Zetian paid to win the Li royal family at that time. Wu Zetian and her four sons, the eldest son, died young, and the second son was terrified because of his superior ability. Finally, Wu Zetian directly framed her son for rebellion and killed him. However, Wu Zetian successfully came to power during the period of Tang Zhongzong and Li Xian, and Li Xian of Tang Zhongzong was banned by Pei Yan because he wanted his father-in-law to be prime minister. It is not unreasonable to be angry that he gave the whole world to his father-in-law, Wei. Pei Yan transferred it to Wu Zetian. Wu Zetian directly abolished Zhongzong as King Luling, exiled Chang 'an, proclaimed himself emperor, made Luoyang his capital, and changed the title of Zhou. It is very unacceptable for her to pass the throne to Li Xian again.
On the other hand, Wu's sons and nephews are not as good as one. It stands to reason that the throne should be given to Wu Zetian's children, but the Wu family did not. After all, Wu Zetian also made preparations. Wu Zetian abandoned his third son, Li, and forced his fourth son, Li Dan, to follow his surname, Wu, and moved to the East Palace to become the Crown Prince.
Finally, it was actually Di Renjie's words that helped Wu Zetian make a choice. Di Renjie just said, "No one has worshipped her aunt in the Imperial Temple since ancient times." . In other words, the emperor did not sacrifice to his aunt, that is, only his son could sacrifice to her every year after her death. Wu Zetian directly decided to return the throne to the Li royal family. Have to say, di Renjie hit the nail on the head of this sentence, and it is also the intention of Wu Zetian.