Why do many Koreans have China surnames?
The ancestors' names of ancient Koreans were the names of the Hu people, with a long list of syllables. After the ancient Koreans were civilized, in order to show that they were not barbarians, their names were sinicized. In fact, there are various forms. Some were given by China, and many minority leaders were given Li by the Emperor of the Tang Dynasty, but most of them were only changed. Just like Aisingiorro's surname in Manchuria, China, according to the simplification of pronunciation, it was changed to Aisingiorro and other China surnames.
Koreans traditionally use the name of China as their name. But now it's a little localized and westernized. For example, Nara, Anglenala is an inherent Korean word meaning country. Another example is tremali. I don't need to say much about it. Mari is a foreign name.