In some 'developing countries' the traditional way of dealing with such behaviour is to ignore it because the victim/victim's family simply hope the trauma will mend itself (as they do not have the skills or support to deal with such situations in an official way) , or due to shame will not pursue it so as not to lose face.
In her country this possibly is 1. not considered a crime or 2. avoided by the police and the victim blamed - particularly if the perpetrator is older and has more to lose. The woman no doubt felt disempowered, and the fact that she was from another country may be why the elders felt it acceptable for this particular brother to teach her son (just a guess).
No doubt the brothers at Bethel are aware of such cultural differences and in this case used those differences to their own advantage.