Whether conscious of that fact or not, being a man is much much harder and requires much more out of someone. Whereas being a woman comes preloaded with tons of protections, free stuff and lower expectations (which means a woman has to achieve less to get the same amount of respect as a man). Also there's a ton of contempt for men in western societies thanks to leftists. So some men who feel like they failed at life, who just want to have an easier life start thinking they could become a woman and... try to do that. Or that's just my theory, feel free to accept or dismiss it.

I think there also was some genetic factor but I can't remember anything about it.