Nicholas Cafardi has reviewed in Commonweal the muddled history of the canonical handling of abuse cases. He answers a few questions, but he says many more can be answered only by the Vatican, which has not learned to be transparent: 

What we do know is that eventually a few curial officials came to understand the insufficiency of official responses to the scandal—and many more couldn’t or wouldn’t grasp its magnitude. Some bishops and their canonical advisers were flummoxed by the new Code; others looked the other way. The Ratzinger who in 1988 sought a speedier canonical process for handling abusive priests delayed decisions to remove them later. The same man who as a cardinal refused financial gifts from the Legion of Christ as pope allowed the order’s abusive founder Fr. Marcial Maciel to fade into a life of prayer and penance. By all accounts, Ratzinger’s awareness of the sexual-abuse crisis evolved over time, not always in a straight line, and often in conflict with other curial officials. Evidently Cardinal Angelo Sodano, John Paul’s powerful secretary of state, worked hard to frustrate investigations into the sexual abuse perpetrated by Maciel. We may never know whether or how Ratzinger fought to break Sodano’s blockade. Likewise, it seems improbable that we will ever know the full story of Ratzinger’s role in the reassignment of an abusive priest during his tenure as archbishop of Munich. The various currents of power in Rome can be overwhelming—even for a pope.

 So we have to continue to try to connect the dots. The resulting picture may in fact be less flattering to the Church (e.g., malice and corruption) than the reality (e.g., dilatoriness and incompetence) – but no one knows, and no one  may ever know.