To understand that the master of the Three Realms is no trivial matter, in name, he reigns over all beings of the Three Realms; the Jade Emperor and the Queen Mother have been sealed by the Heavenly Dao's first Saint, Hong Jun Daoist.
Putting it bluntly, where the Heavenly Emperor's will extends, even the Western Lingshan must obey without the slightest dissent.
However, once the Jade Emperor was weak and forbearing, he also dared not command the Three Realms; but Ye Xuan was decidedly not the Jade Emperor—if he became the co-sovereign of the Three Realms and issued a Heavenly Emperor's Dharma Decree to Lingshan, what should Duobao Tathagata do?
This concern was just one aspect, but what troubled Duobao Tathagata the most was that the Heavenly Sect Master, disregarding the thoughts of the other Saints, sealed Ye Xuan as the Three Realms Emperor in an extremely domineering private decision. This also meant that the Sealing God Tribulation of yesteryear would once again be replayed.