Jerry Slevin, a “retired Catholic and Harvard schooled international lawyer” asks the question and offers a very plausible explanation.
In his blog http://christiancatholicism.com/ Slevin explains it this way:
Pope Benedict XVI for the first time publicly shamed a voting Cardinal, Mahony of Los Angeles. The Pope’s pawn, Archbishop Gomez, publicly referred to Mahony’s child abuse cover-up conduct as ‘evil.’ This unprecedented and selective public papal condemnation, in my view as an experienced retired lawyer, significantly increases the risk for Mahony that he will yet still be criminally prosecuted, possibly for obstruction of justice or perjury. Prosecutors now have a papal blessing to go after Mahony. Yet the Pope has also just permitted Ireland’s voting Cardinal Brady to exit gracefully, without papal condemnation. Brady was reportedly involved in priest abuse cover-ups at least as ‘evil’ as Mahony. Why the different treatment for two Cardinals?
The likeliest explanation is current papal election politics. Conservative Cardinals in the Vatican clique, including American ones like Burke, Law, Stafford and Rigali, and their right-wing U.S. Republican contributors, have for years targeted Mahony, often an ally of U.S. Democratic political leaders, as an obstacle to the Vatican clique’s efforts to maintain Vatican domination of the Catholic Church worldwide, through groups like Opus Dei that Gomez and convicted criminal Bishop Finn are members of. Brady, on the other hand, supports domination by the Vatican clique, as evidenced by his acquiescence in the current unchallenged attack on one of Brady’s most popular priests, Fr. Tony Flannery, by the Pope’s new German Inquisitor. Flannery’s brother is a top ally to Prime Minister Enda Kenny, who has strongly opposed papal domination in Ireland.
The signal is clear. The Vatican is prepared, it appears, to use selectively the criminal prosecution risks inherent in the worldwide abuse scandal to intimidate voting Cardinals……