Why do hundreds of family surnames start with Zhao Qian Sun Li? What is the allusion?

The first is Zhao:

"Hundred Family Surnames" first appeared in the Song Dynasty. At that time, there was a scholar among the people who had nothing to do at home, so he read, practiced calligraphy and annotated at the same time. Some classical collections. One day one of his students asked him how many surnames there were in the world and what they were. He couldn't answer and was laughed at by the younger students. Instead of scolding the students, he fell into deep thought. Indeed, at that time, there was no book or person that had compiled the surnames across the country. He believed that the surnames of all the people in a country were equivalent to the map of the country, which was indispensable, so he started to do this.

He collected all the surnames around him, all the surnames he knew, the surnames that had appeared in history, and the surnames others told him. He recorded all these surnames, and gradually he collected them. Later, the emperor at the time heard about this incident and wanted to see the book he had collected recording surnames. He was very happy but also very frightened. So he carefully checked his records all night long to see if there were any errors. In the middle of the night, he fell asleep at his desk and dreamed that he was being beheaded because the emperor said he was going to rebel.

After the old gentleman was frightened and woke up, he was puzzled. As a commoner scholar, how could he commit rebellion? Then the problem must have appeared in this book. He checked it carefully, and it wasn't until the moment he was about to hand it in that he realized that he had written his last name first! So I quickly changed it and wrote the emperor's surname first. During the Song Dynasty, the emperor's surname was Zhao, so Zhao became the first in "Hundred Family Surnames". Secondly, Qian Sunli

In a hurry, the old man only changed the emperor's surname to the first one, and the rest remained unchanged. After this book was passed into the hands of the emperor, it was highly praised and spread among civil and military officials. Those dignitaries opened it to see if their surnames were there, but it took them a long time to find them. This made them very dissatisfied, so they asked the old gentleman to re-rank them so that theirs should be ranked first. At that time, in the Song Dynasty, in addition to the emperor's surname Zhao, the three surnames - Qian, Sun, and Li - were the surnames of the most prominent nobles at that time, so the surnames of hundreds of families began with "Zhao, Qian, Sun, and Li".