They joined the clergy (Catholic and otherwise) for the same reason they became scoutmasters & teachers: easy prey.
During the height of the scandal the Catholic League reported five incidents in five days in NYC public schools - and it received NO coverage. At least the Vatican has banned “celibate” deviants from the seminaries; that was long overdue, and cost them millions (on top of the faith of many of the victims).
just the victims? more people than that I fear.
Just as Judas was one of the 12 original apostles, evil was following Our Lord.