Child abuse by priests: A mystery that must just be believed?

There has long been a tradition within Catholicism of ‘explaining’ the unexplainable by calling it a mystery.

The doctrine of the Trinity, for example, the three divine persons in the one god is a mystery; you just have to believe it.

Now I see the Pope has described the Catholic Church child abuse holocaust as ‘a mystery’.

How are we to explain the fact that people who regularly received the Lord’s body and confessed their sins in the sacrament of penance have offended in this way?

It remains a mystery.

Ok, I know they’re different kinds of mystery but can it be long before the ‘mystery’ of child abuse is incorporated into the official doctrine of the Catholic Church?