Why did Mi Yue have an affair with Yiqu Wang for 30 years before he was murdered?

After 30 years of adultery with Yiqu Wang, Qin finally came out of the civil strife, and the weak Qin became a weak one, leaving the six countries with no resistance. At this time, the national strength of Qin increased greatly, and there was no need to fear the threat of foreign songs. So Mi Yue chose an auspicious day, lured Zhaili, the king of Yiqu, to Ganquan Palace, then made a surprise attack in Gentle Township, killed Yiqu King, immediately sent troops to destroy Yiqu, and pocketed all the territory originally belonging to Yiqu King. Since then, Qin not only expanded its territory, but also had no worries about its western border, which laid an important foundation for its descendants to seize power, sweep Liuhe, unify China and become the first emperor.