When interviewed, convicted child sex-offenders admitted to being very particular about the children they chose to abuse. They looked for children that were loners or seemed less-confident and in need of attention/affection/love. They exploited this need, showing interest, making the child feel loved, and in turn used that emotional connection to perpetrate their bodies. The children were less-likely to tell because they did not want to sacrifice the relationship or because they had less respect for their bodies.
Even worse, when known, a perpetrator may target a child known to have been abused previously. Even with therapy, it is not a guarantee that the child has overcome the mental and emotional damage from the previous abuse, and may be more likely to not defend themselves against the advances of a new perpetrator.