When Qi Jinggong was in power, the office was corrupt. Tian borrowed money from the Big Dipper and recovered it from the Big Dipper, which made "Qi people return to the flowing water" and increased their household registration and strength. This is the so-called "abandoning the people and returning to the fields". In 489 BC, Qi Jinggong died. Qi and Gobang established Gongzi Tea, and the Apocalypse pursued Gobang and Gobang, establishing Gongzi's health and self-reliance. Since then, Tian controlled the politics of Qi, gradually controlled the political power of Qi, and finally replaced Qi.
The earliest royal family in the state of Qi was Jiang Lv, and Tian replaced Lu. After long and complicated repeated struggles, peaceful evolution and armed struggle emerged, sometimes hidden and sometimes open. But as early as when Yan Ying and Chu met, Yan Ying, who witnessed Tian's behavior, once said, "The government of Qi belongs to Tian".
These reasons are obviously related to why the country name is not changed. During the Warring States period, the Zhou royal family moved eastward, which had two key points: the enfeoffment system still existed, the Zhou royal family still appeared in the world, the essence of kingship and the existence of the son of heaven.
Just like the appointment of the Prime Minister by the Queen of England, although this has nothing to do with the real power of the royal family, as a part of the "ceremony" recognized by the world, this ceremony is indispensable to the legitimacy of the Tian regime. It concerns future generations, and there is no right or wrong. You can also see Tian's judgment here.