Seven Calamities Ghost Immortal, Pei Xuanjing, with his Martial Arts power, wouldn't necessarily be inferior even if those old monsters hidden in this realm were to appear.
So why would he actively get involved when there was no threat?
Pei Xuanjing indeed intended to use this as a breakthrough point, but his focus lay on the situation of the Great Thousand Worlds, not on a mere Da Ye Dynasty succession conflict worth his attention.
To Pei Xuanjing, the struggle for the throne of Da Ye Dynasty, although not child's play, wasn't particularly powerful in his eyes either.
For Pei Xuanjing, it was merely an entry point to interact with those behind the princes, not to collaborate with the princes themselves.
To put it bluntly, with Pei Xuanjing's power, whether it was his True Immortal essence or the displayed combat power of a Seven Calamities Ghost Immortal, those princes were not qualified to collaborate with him.