I don't know, I think it's kind of amusing that a year of godhood and doing what he likes most (making people suffer and blowing trout up) made him bored and realize how utterly meaningless life is. I sometimes wonder, if the game was remade or got a modern Ultimania, the writers might reason that Kefka lost the battle because he let them, since he kind of became a nihilist due to being a god.