There is a reason for everything, just as their usually is a stimulus for everything, even if it's not realised at the time, some period after etc. The stimulus may be positive or it may be negative. It doesn't necessarily have to produce a pleasurable response at the time. But it's usually more than one stimulus. Much like the Wave Theory in physics.
As for the genetic? It could be possible, as everyone has preferences. Psychological tests that have been undertaken to discuss the theory of 'Blank Slate' vs Innate have shown that even babies show preferences after adapting to a certain type of stimulus.
So are preferences innate? In a way yes. It's how we are wired up, so people might prefer some elements in BDSM..not all elements, I can't say that the idea of nipple torture turns me on, it doesn't, but to others it does.
That being said, I can say that if I backtrack a bit I can say that my very first 'stimulus' was being taken out to the cinema with a group of adults one evening (this was the 70's), the movie showing wasn't an adult movie, however one feature that 'shocked' me (or made me sit up and take notice) was the fact that this man completely overpowered a woman physically, slapped her a couple of times and then she gave in. No nudity, no 'simulated' sex, it was just for one kiss, but that image I remember now when I'm 32, and I saw it when I was 6. The other aspect is the fact that my father was a very big man, tall and imposing, but not violent or verbally abusive to my mother, but I remember his stature but I also remember his capacity for losing his temper (not to me) but in general. I had a very good relationship with my father, he had a lot of time for me and respected me as a child, however over the years there have been snippets of images like that when I was 6 years old, and I add it all up, especially after not being satisfied in some relationships or having relationships completely disintegrate, and I realise it's because I'm not the 'domineering' game playing woman, I need a man to be a 'man' in terms of Domination and I don't mean a few slaps on the ass while I'm giving fellatio, that's just too stereotypical and has nothing to do with BDSM in my mind.


So sure, there is always a catalyst.