Lured Into A Trap?
He thought a goddess like her wouldn't care about mortal things, but only now he realized that he had yet to understand her thought process. She may not care about mortals like mortals do, but she does care about her own creations, especially this world, and seeing it in a dying state must be no different than how a parent would feel seeing their child dying. And since the reason for this world's poor state might be related to her sworn enemy, it only added more fuel to the fire.
He was actually surprised she didn't seem to hold any personal grudges towards him for inheriting the legacy of her sworn enemy. Considering the mentality of the cultivation world, where people would annihilate every ancestor, descendants, and even the chicken of their sworn enemy, Luna seemed to be on the far better end of the spectrum.