he wouldn't. he really thinks he's god's gift or something
I think the evil energy is messing with his mind and somewhat controlling him subconsciously. So even when he notices he can't stop. Also I've heard in other stories and things that black magic is like an addiction like with the bird he can find himself using it even without his knowledge because he's begun to need it and it's begun to control him. Also it's alters his mind. And then there's the reference to it being demonic energy which means even more so something could be trying to take him over or convert him and even if he wanted out he says he couldn't because he thinks only he can save the empire and the people because only he sees the issue. And that he has had some divine revelation even though those same thoughts show he hasn't and that he has no belief in his own God.
He's long past that stage, unless a miracle happens. The evil practice made his insanity even worse. He'll be a tough enemy for sure.
I hope this priest come back to his senses