First, there were hundreds of thousands of people under Zhu Yuanzhang, who were confident and ambitious and forced Zhang Wuji to meditate. Second, with the contradiction between Zhao Min and King Ruyang, Zhu Yuanzhang later said that Zhao Min was Zoroastrianism now, and her father was a marshal of military forces in the Yuan Dynasty. At the last moment, is Zhao the expert blade father and brother? Why did Zhang Wuji dare not kill Zhu Yuanzhang? Because Zoroastrianism aims at restoring the Han people, it is not difficult to kill Zhu Yuanzhang at this time. The infighting of Zoroastrianism will give the Yuan Dynasty a chance to fight back, and the excellent situation of resisting the Yuan Dynasty will be destroyed.
Zhang Wuji's personal leader's position is small, and the welfare of the whole world is big, so Zhang Wuji can't kill Zhu Yuanzhang. Mr. Jin Yong refused to let Zhang Wuji be emperor because it was inappropriate. The biggest reason is Zhang Wuji's carefree personality, which is easily disturbed by the outside world.
Not necessarily "no ambition". Most of Zhang Wuji grew up in seclusion. In order to conform to the consistency of the characters before and after, Zhang Wuji can be the leader of Zoroastrianism because of the situation, but he can't become Emperor Zhang. Loneliness is a real loner, and his character must have a lean and changeable side.