Hadriel: Seems like most of these situations are with those whose offense happened in the 80's or before the mid 90's. At least it appears that way.
They may have been lost in the shuffle
I have been following this on reddit
This man was in prison when he was converted by JWs. They knew he was a child rapist. When he was released, he became a good, active JW - so good in fact, that the elders allowed him to do activities with kids (except the elder's kids)
He wasn't lost in the shuffle - he was groomed by the elders themselves while he was still inside his jail cell and then, after he was released, the elders 'kept an eye on him'
According to reddit...I think I have the gist of that part