The thing I think is interesting abut the Catholic BDSM (Catholicism predates Islam) is that Rome was all about dominance, overpowering and controlling populations by force and enslaving.
Grassroots Christianity threatened the Empire so it converted to Christianity to keep some sort of hold over the population, which became the Catholic Church. (There's a good BBC documentary by Bettany Hughes at the moment talking about how Rome was a kind of 'death' worshipping cult, putting a minor god -Mars - the god of war up in the prime position). Because Christians were total pacifists, it took the concocted concept of 'holy war' to mobilise Christians into Roman belligerence.
So the Catholic Church absorbed some of the Roman 'death cult' into its practices.
Islam is also a religion spread by belligerence and Islam literally means 'submit' - so no surprises they are into BDSM too.
The phenomenololgical content of BDSM fantasies are likely , imo, rationalisations and coping with echos of real life trauma of bondage, domination, forced submission and subjection to pain. It suits the beneficiaries of the status quo to have people wanking off to pretend and play abuse, torture, enslavement and humiliation. It minimises the seriousness of it in real life.