The position of the Emperor of Heaven had never been an easy one, especially for those who desired to be the sole authority, proclaimers of the celestial mandate, rulers over the heavens and earth, and the Eight Desolations and Six Harmonies.
Let alone Zhu Houji, even if it were Pei Xuanjing who took the position of the Emperor of Heaven, he too would find it difficult to suppress all dissent and unite the entire Heavenly Court. It was impossible.
Even if Pei Xuanjing had enough power to suppress all dissent, the relentless rebellions would continuously wear down his time and energy, delaying his cultivation. Therefore, Pei Xuanjing didn't care about the position of the Emperor of Heaven.