You know, I've often wondered about this, as it - at least intuitively, on the face of it - doesn't make a lot of sense for someone who has clearly been sexually abused to fetishize... being sexually abused, basically. The human psyche is such a weird, weird thing - but this is KF, so that more or less goes without saying. This place is a grotto to human derangement.
I wonder, though, if it's like some kind of crude, self-induced exposure therapy?

sort of like the way children who are terrified of dogs will be brought to guide dog training facilities
(I had a childhood friend whose fear of dogs was helped by this) for controlled exposure to their phobia trigger. I've heard of versions of this method being used for other triggers. Obviously it's not conscious in this case, but I wonder if it's a way for them to recreate what traumatized them in circumstances where they can tell themselves they're in control?
It just seems like way too common of a pattern in FtMs and other transparent kiddy diddling/rape victims to be a coincidence.