Pope Benedict’s health was failing, and he did not think he was up to the task of cleaning up the filth described in the report. This is completely believable to me.
Benedict is a brilliant man, but does not have a lot of administrative skills. It has also been reported that his own Secretary of State, Cardinal Bertone, was actively working against him.
Bertone was the number 2 man in the Curia under Benedict. My guess is that he was blackmailing certain prelates known to be active homosexuals, who often were also prodigious fundraisers. Basically, the Curia have been practicing a modern version of simony, the same kind of corruption that so inflamed the Protestant Reformers.
Simply, sodomy simony.