Can you please explain how and why who were sexually abused in childhood masturbate obsessively?

See below: I am not sure these two topics are related. You might want to discuss this with a psychologist or psychiatrist.

Variable responses: Some of my sexually abused patients have masturbated compulsively. For several this has been a way to self-soothe, under their own volition rather than someone else's. For others it has been a way to experience themselves as still intact despite previous experiences. Others have not wanted to acknowledge their sexuality at all. So, the response is variable and never an automatic one.