Since as you say, the trans phenom is not evenly distributed but occurs only within specific demographic groups, I think it's important not to lump them all together under the heading of "social contagion."

For the girls and teen girls and young women who are coming out in droves as trans and non-binary and gender queer, yes it seems to be driven by social contagion - and an entirely new social contagion at that. Hence, in teen girls' friend groups, a whole bunch of girls will "come out" as trans (or whatever) at the same time. They are encouraging each other to be trans, and teaching and coaching each other on exactly how to go about it, just the way girls used to teach each other how to be anorectic and bulimic.

For the kids being transed by their parents and other adults, the parents seem to be involved in a social contagion, but the parents' underlying motives are narcissism and attention-seeking, sexism, rigid beliefs in and adherence to strict sex role stereotypes, a desire to control their kids, and homophobia.

For the homosexual men who want to bed straight men, the fad of going trans seems to be partly due to social contagion, but mostly it's driven by their own internalized homophobia, extreme narcissism, their total immersion in their own fantasy lives, and a weird combo of their own overwhelming sexual needs and compulsions that drive them exclusively to desire straight men alongside their total inability to grasp and accept the basic truth of straight male sexuality - which is that straight men want females, not males pretending to be the opposite sex. But most of gay guys who become trans develop their sexual tastes and compulsions on their own and in secrecy at a very young age; they're not picking this stuff up from other boys the way all the girls/young women with ROGD are. Though nowadays these boys are of course being heavily influenced by new trends in online porn and the fact that being trans has become a powerful new sociopolitical movement that provides trans-identified people with all sorts power, privileges and benefits.

As for the huge number of heterosexual boys, young men and full grown men going trans, they are driven by male sexual compulsion and narcissism of autogynephilia. AGP is of course now been spurred heavily by online porn, LARPing, the internet etc, and that's why it's becoming more widespread and visible. But the condition existed in a significant % of men long before the current era and the new technologies of modern telecommunications and social media.

The AGP impulse originates within the psyches of individual boys themselves during early puberty, and it's in early puberty that their lifelong AGP tendencies and habits get cemented. However, when AGP youths start imagining themselves as females and using items of "female" clothing & intimate care as masturbation aids - and they find it gives them massive boners and the super-orgasms they call "gender euphoria" - they almost always do so entirely on their own and in total secrecy. And as adolescents, these boys' AGP usually causes them to feel a great deal of isolation and shame - and bad as the shame makes them feel, their shame also enhances the erotic pleasure they get from their AGP. Only after these guys have been stealing women's undies and intimate products to jerk off in and to and this has become their fixed pattern do they find other males with the same proclivities to egg each other on and bolster each other's entitlement and power.