The motivations of child sexual abuse are wide and varied, and usually amount to someone with a legitimate mental health need that they are attempting to meet by sexual behavior with a child. The mental health need and the things that make the person a risk to children vary widely. Sexual abusers are juveniles almost as often as they are adults.
Some of the motivations for children with sexual behavior problems, which Elizabeth Letourneau covered at the Moore Center Symposium in 2017 are:
That is just a partial list of motivations for children with sexual behavior problems who cause trauma to younger children. The partial list for motivations in adults would be very similar, and encompasses a wide range of needs that could be met in other ways. The youth or adult who lacks knowledge of consent or legal boundaries can be educated, and in so doing prevent victims before they happen. The youth or adult with a preoccupation with sex can learn how to manage their sex drive in healthier ways. Youth or adults who abuse substances can get help with addressing their behavior.
Knowing the motivations for child sexual abuse helps us know that prevention is not only possible, we have specific areas in which we know prevention to be effective. By addressing the underlying needs present in these motivations, we can stop sexual harm before it occurs. It is the need to address many of these motivations that the prevention recommendations of this site (and many organizations) are based upon.