What does Job have to learn? He has not sinned, but he is not humble. Job's life is the Dark Night of the Soul. He is learning perfection.
The same is true of St. Paul, who was not sinning, except for zealously killing Christians, but he was loving the Lord. He had more of an enlightenment, rather than a conversion. His enlightenment was that God was the Trinity and Christ revealed Himself to him. He came into the Illumination Stage after his eyes were darkened, a sign of the Dark Night.
The Dark Night is the time we become, finally, humble. These ideas were given to me by a seminarian, who has been reflecting on Job, Paul and the Dark Night.