User blog comment:Miskos3/Fairy Tail 527: Emotion, Review/@comment-24039234-20170317165250/@comment-7418318-20170318115955

As the story stands right now neither we nor Zeref truly know if it really was a divine intervention that cursed him.

It's quite possible that the curse, rather than the will of a god, was some natural phenomenon and the whole "god of life and death" stuff could just be superstition of people who blamed it on the divine, because they couldn't figure out how it really works.

Just like our ancestors used to believe that a god (be it Ra, Apollo, Amaterasu, Sol or whatever) personally made the sun rise above the horizon of a flat Earth each day until we found out that it's all a chain of natural phenomenon.