The real (read internal, here) is not so much moral as administrative. There is a great shortage of priests, to begin with. Doctrine from the Early Middle Ages states that a priest is only a man, no more moral than any one else; that a vocation is a gift beyone merit. Add to that the fact that, for decades, the Curia has been nervous about it's diminishing moral authority and you have a situation where head in the sand blindness becomes almost mandatory. The Church likes having people look to priests and has done it's best to promote this attitude. Unfortunately, that included turning a blind eye to felonies.