That's ignoring that the modern wave of transgenderism is largely a social contagion, there's books written about this. It's a trendy thing among young people and is literally propagandized to them in school & media, which is why it's highest among zoomers.
Porn probably doesn't help, especially all the weird porn that makes tentacle hentai seem boring and normal by comparison, but to lay this disease at the feet of pornography alone or even primarily seems incorrect to me. The ubiquitous nature of porn and its popularity doesn't make mesh with how relatively rare transgenderism is, though it's a big problem there's not THAT many trannies. It seems to be one of those correlation =/= causation things.