As a parent, if it was my kid I would go straight to the police and or
beat the living shit out of the perpetrator. Were all these parents of
the victims brain dead or that indoctrinated?
I understand that as parents people must want the well being of their children to come first. In the particular case of the WT cult, those parents are conditioned to not question their authority, also mislead to believe that the elders and the WT itself are properly capable and prepared to deal with those situations. Additionally, they are to blindly trust everything and anything they say, including letting their own children die over a blood transfusion issue. This is not the only cult that has to deal with sexual abuse of children and parent being unwilling or unable to properly deal with the cult leadership stance and actions over it. In fact, the WT is by far not the worse when it comes to this type of situations.
Then, there are the other things to consider when you factor out the WT and their negative influence. It is well documented that there are a rather large number of parents who don't believe and/or don't provide support to their children when they express that they have been sexually abused. According to experts, the most common reasons for that happening have to do with the parents' fears of them being held responsible, along with a whole lot of other reasons, most of them around the parents caring more for them as individuals before thinking of them as parents.
Remember, perpetrators normally are people who are close to the family, sometimes they are family members. Also, in the case of the WT and other cults, the perpetrators are (or are perceived as) people with a degree of power over the parents. There can be repercussions in the community where they belong.
Speaking of repercussions, some parents prefer to cover it up to save appearances. They figure that the "shame" and labeling their child as "molested" will carry a social burden for the rest of their lives and they figure it's better if that doesn't come up to light.
As you can see, it first glance it seems like a no-brainer to have a person arrested and a child protected, but in reality there are other factors (real or perceived) that can make parents think twice before taking actions. I'm not saying that that's good or bad, it's just how it is.