The Cult Of Maciel

Rocco has some useful background here:

Until the practice’s dissolution in 2007 at the behest of Pope Benedict, even criticism of Maciel by Legionaries was banned under a secret vow made by members of the society.

The key thing to understand about the Legionaries is that they were ultra-right-wing and brought in lots of cash to the Vatican. Hence they were allowed to run an international child-abuse ring, and got cover from both Popes to get away with it.