I don't understand how they thought they could pull off a hoax such as this.
They certainly didn't foresee a future in which this information could be widely disseminated on devices that didn't even exist yet, over a network of information that didn't exist either, and have any number of people connecting the dots. They also may not have foreseen a Church in such dysfunction, that people would ask the awkward questions and not be afraid to do so, rather than thinking "we cannot dare question anything that priests and bishops tell us is true".