The accusations were made 20-30 years after the alleged abuse.
And though defrocking would have been the appropriate response when it would have actually meant the priest would have no further exposure to children. It would not have done so at the time of the letter to the Vatican. And if the accusations had been recent, yes he the Vatican should have taken steps to defrock him.
And nothing that happened prevented either civil or diocesian authorities from investigating, charging and trying Murphy. I agree both should have. I do not know why the civil authorities declined such action. But believe the Diocese did so in a very misdirected desire to protect the Church. Which was wrong, is wrong and always will be wrong.
So yes there is plenty of fault to be found here. But it is not with the Vatican for declining to initiate a canonical trial 40 years after the violations occured and 20 years after any other investigation into the matter.
Fair enough.