Now that I think about more. Maybe. As Mambo Jambo theorized.
When when the sun left, they stopped balancing out the shadows. That's when/why they corrupted Macaque. After Wukong left because he was balancing Macaque out.
That also might make sense depending on the S5 Memory.
If Wukong had already left, and that's when the shadows corrupted Macaque. He wouldn't know what happened.
It would make sense on why Wukong didn't want to fight him. + them used being best friends and post fight, they probably both wanted to at some point make up.
But in the end Wukong had ended up killing and blinding his eye and sealed him in Diyu because Macaque was out of control.