I do not believe in the motivation, which they claim drives them; call it a sense of self, or personal identity, or some call it the soul.
Soul has nothing to do with sex, or gender.
Most older heterosexual males who go for this lack basic trust, and at puberty the drive is too strong to share with another, so they dress up as their sex object and years later, think it is thee real self. They would be better off being transvestites, or cross-dressers
Some females think being a women is oppressive, they want to pass as male, more than change genitals.
A few homosexual males who are small think they can get a more dominate straight man being a female, they never tell. Some do fine when young, but loss of beauty and relations with men leaves them living empty lives.