crippling body dysphoria and crying for hours
Most preteen and teen girls go through this. The brain rewiring and hormone changes, startling body changes, your body making you a target for frightening men, and feeling under massive pressure to look perfect, make millions of girls hate their bodies and cry for hours. Add in ASD, being gender non-conforming, sexual abuse or other trauma and girls are even more likely to feel overwhelmed and an enemy of their own body or not acceptable as a girl.
Now add in an attractive, tempting ideological movement that praises and elevates kids for "coming out" as "trans", tells them trans is beautiful and cis is boring, and gives them instant kudos, power (as everyone's scared to upset them), and a special "oppressed" group to be part of so they're now cool. Of course a lot of the most vulnerable, suffering, excluded or picked-on kids are going to be drawn in. They're the same kids who previously had to find their way through the misery of puberty and not fitting in, and came out stronger.
Having all these feelings doesn't means you're a boy/man. It means you're being told you can be one when you can't and this this is the answer to all your problems.
And that wouldn't be so bad, if it really was just about "gender" - if being "transgender" was just a pretty sexist way of describing departing from stereotyped expectations. After all many girls, often lesbians, do that anyway.
But no, this special status comes with getting on a pathway to permanently alter and generally harm your body and set yourself up for lifelong health problems, which a good number will regret as they were too young and immature to understand this. That's why it's bad news. You can't change sex, but these kids are being led to believe you can and that it will help them. Why?