This is divine will.
The arrival of their mounts was also to perfect the Calamity of Measurement and allow it to reach Perfection.
However, they had not anticipated that Sun Wukong seemed to know everything.
Even if Sun Wukong had reached his full potential, he was merely one of four, what could he change?
Nine Spirits Holy Yuan fell silent, apparently considering Sun Wukong's proposal.
After a while, the old fellow finally reacted, huffing coldly as he said, "Humph! I nearly fell for your trick, young man. If you want me to join you, then wait until you truly have the upper hand!"
Having lived for so many years, Nine Spirits Holy Yuan naturally worried he might bring a huge crisis and trouble upon himself by carelessly choosing a side.
Although now Sun Wukong seemed to understand everything and appeared to have done something behind the scenes, these minor actions were probably like an ant trying to shake a tree, insignificant compared to all the Immortals and Buddhas.