At the time of his resignation I said that on one gives up that much power, wealth and unquestioned adoration just because he feels "tired." It was perfectly clear something was rotten in the Vatican. Here are some more details on this story from another source:
The Panorama weekly and The Repubblica daily newspapers reported that Benedict's decision to resign was triggered by the secret report compiled by three retired cardinals. The report allegedly contained details of corruption and of blackmail attempts against gay Vatican clergymen, as well as favouritism based on gay relationships. Both publications quoted a source with knowledge of the investigation as saying that the cardinals' conclusions "revolve around the sixth and seventh commandments," namely "Thou shall not commit adultery" and "Thou shall not steal." Referring to the upcoming papal election, Lombardi said there was "unacceptable pressure to condition the vote of one or other member of the college of cardinals, who might be disliked for one reason or another".