Why did Wei Zi and Er Kang leave Swallow at the end of Princess Zhu Huan III and live with Swallow in Dali?

After all, Wei Zi's father and grandmother (Galeries Lafayette) are in the palace. She wants to go back to filial piety, Erkang wants to be loyal to the emperor, and Mei goes back to give one million yuan to Yu Fei and Xin Rong, and she will be carefree in the future. Swallows are broad-minded, and it is impossible for people with feudal ideas like Yu Fei to really accept swallows. Swallow is also very sensible. She feels guilty that Fei Xinrong asked Yongqi to go back to her filial piety and made a two-year contract.