That's because those are, for the most part, staples of the coming of age story. By inserting transitioning as an act of emotional/mental maturity, they try to make the outside observer believe that their transition led them to become different persons, growing as individulas thanks to it. This is of course a lie, they want to transition to reroll their infancy and rewrite their pasts, that's why they all behave like children and focus so much on children's media, not because a concept so absurd as "trans kids" exists, but because they wish to return to being kids. They see themselves as the kid getting groomed, as vaushniate philosophy would put it.