There are a lot of ways to get off on rapefic, ergo a lot of people write it.
And while I haven't done any statistical analyses either way, I've gotten the strong impression that fandom as a whole has a much higher proportion of assault and abuse victims than the offline world, and/or a much higher proportion being open about it*. People often have to suppress their assault/abuse histories in real life, so fandom becomes one of their only outlets to let out anything from frustrations to commiserations to celebrations that are in any way related to assault and abuse, or recovery from them.
* = I presume. I'm one of those rare cases where I'm perfectly fine talking about my assault in real life but I can't talk about it in fandom.
Pretty much this
And while I haven't done any statistical analyses either way, I've gotten the strong impression that fandom as a whole has a much higher proportion of assault and abuse victims than the offline world, and/or a much higher proportion being open about it*. People often have to suppress their assault/abuse histories in real life, so fandom becomes one of their only outlets to let out anything from frustrations to commiserations to celebrations that are in any way related to assault and abuse, or recovery from them.
* = I presume. I'm one of those rare cases where I'm perfectly fine talking about my assault in real life but I can't talk about it in fandom.