Why can wuyue be king and Qi Jin not?

First of all, the history of wuyue is extraordinary.

The first generation monarch of Wu was Taibo, the father of Gu Gong, the leader of Zhou tribe, and the eldest son of his uncle. Because Zhou wanted to pass the throne to his youngest son and his son Ji Chang (that is, Taber and his third brother), they fled and changed their names to Wu. Wu Taibo is regarded as the ancestor of Dongwu culture by later generations.

Therefore, Wu is Zhou's big imperial clan, and it is understandable to be king.

Yue claimed to be a descendant of Dayu, that is, a Xia immigrant. At first, they were not within the scope of Zhou's management, so they said it was entirely their own business not to look at Zhou's face. In another country, Chu was the first king. Chu was made a viscount. Later, when the territory expanded, the emperor needed to seal it, and he became king himself. This also shows that Zhou's control over the world has actually existed in name only.

We can also see a pattern here. The earliest disobedience to the king was basically in the border areas, and the Central Plains countries like Qi and Jin did not have the courage to check and balance each other. Anyway, whether they are kings or not is just a matter of name, which doesn't affect their position among princes at all.