Dunno. I'm not sure why any fetishes exist. And I very much doubt you'll ever be able to figure out a singular cause.

I would expect that it is some kind of pavlovian response. There's some academic research on it. Blanchard I believe studied this specifically and coined the "autogynophilia" term.

Its existed in some form in the past but seems to have been limited. I actually don't think it's all that common, but it's common enough that we aren't talking about, one in a billion people, but maybe something like one in a thousand. After that I think it simply progresses much the way any kind of sex addiction, or addiction in general progresses.