You need to separate a couple of things, getting a paraphilic fetish and the selection of it.
Too many people look for a single event or experiences to figure out what happened to cause the fetish, in this case diaper fetish. But it does not work like that, everything does not come together at an event and create the fetish. First you become susceptible to getting a fetish then your mind fixes on something, perhaps by the chance of timing or more likely a couple of things. Then it imprints on it and your stuck with the fetish.
This explains why 2 people can go through the exact same treatment and one comes out with a fetish and one does not. First something happened, perhaps it was the brain injury or the bout with epilepsy then I later but still at a young age fixated on a couple of things. The diaper perhaps because I got put back in diapers for wetting the bed then a couple of years later the enema perhaps because I remember getting at series of them in the hospital before a procedure.
I am convinced that had it not been the diaper I still would have got a fetish for something else, so it is not so much what caused the diaper fetish but what caused a fetish at all in the first place, the diaper was just chance I imagine.
I guess I am lucky, I am glad I don't have a fetish from something illegal or that hurts someone. I only have to worry about embarrassing myself.