1, Cao family is a famous family in Jiangnan.
Cao Xueqin's grandfather's family was very prominent at that time, when Cao Xueqin's grandfather was the director of the manufacturing bureau. By the Qing Dynasty, capitalism had just begun to sprout, so capital converged quickly. It can be seen that Cao Xueqin's grandfather's family was quite rich, and it was necessary for Kangxi to go to the south of the Yangtze River, because the emperor spent a lot of money on food and clothing, and in the Qing Dynasty, the centralization of China's feudal system reached its peak.
Therefore, we need the financial support of Cao family. What's more, if the emperor stays in the Cao family, it will be an honor for the Cao family and will bring greater benefits to the Cao family. Therefore, the Cao family is very welcome to the emperor's residence. After all, China has a long feudal history, which makes the emperor's authority unparalleled.
Kangxi trusted Cao Jia.
Kangxi was able to stay in the Cao family when he was in Jiangnan, mainly because of his trust in the Cao family. Because Kangxi trusted Cao Xueqin's grandfather not to put him in danger, it can be seen that Kangxi and Cao Cao still have a very deep friendship.
To sum up, China was always a feudal system in ancient times, and the emperor was the absolute master of China, and in ancient China, the emperor was very noble. Because it is said that the emperor is the real dragon emperor, it is said that the emperor's food and clothing can't be the same as ordinary people. Moreover, according to the strict hierarchy in ancient China, the emperor's food and clothing level was also very standardized. So it makes sense for Kangxi to go to Jiangnan and stay at grandpa Cao Xueqin's house.