I think there's a lot more to it than just that. But I do think tomboys and for lack of a better word Sissy boys are targeted.
I grew up in a time where nobody cared about this stuff. Doing girl things and boy things was just things that we all did the 90s was a different time but in a lot of ways it was better.
I think a big component of this probably the largest one is social media.
Oh, the kid wants to be called Polly or Holly or Jolly or Folly or Billy or Gilly or Willy? Who the hell cares? It doesn't change their sex.
What kids need is guidance and parenting, not "affirmance" And support should mean "however you feel or act, you're fine - your body is yours and it's fine - there is nothing wrong with it." Being a boy is fine. Being a girl is fine. And, being a boy who is effeminate is fine, and being a girl who is butch is fine. Those traits don't make you the opposite sex. Learn to live life and accept oneself as is. That's much better than "navel gaze all day long and wonder if you're a girl."
I think the most important thing you can do to affirm your child is tell them you can never change your sex it doesn't matter what you do but since you were born as will be the sex you die as when someone digs up your bones a thousand years after you die they'll know what sex you were. Of course you tell them I will love you no matter what because that's true or it should be. And if they're a boy and they want to be a little more effeminate that's fine same with girl and vice versa.
The trans thing seems to be coming from social media. They learn the lingo to describe concepts they probably never had. And there are adult people are there giving them this information.