Girls are more likely to be undiagnosed if they are autistic. They are sometimes gender non conforming. They can find it difficult to understand their own emotions, and be way behind their peers in terms of emotional maturity. It is not hard to see how a lifetime of not knowing why it is you don't fit in and suffering hugely with anxiety, you would think you have been born in the wrong body.
There have been some very eloquent autistic women on these boards who have described how they would have done anything to change gender when they were in their twenties. But it wasn't a possibility. They are all glad that it wasn't.
Now it is seen as a human rights violation to deny medical transition and transphobic to consider other therapies for dealing with the distress of gender dysphoria, or to look at alternative explanations.
Coupled with social media normalising and celebrating body modification, it's a perfect storm.
The actual human rights violation is the sterlilsation of non-conforming / non neurotypical young people, the majority girls.
But the overall rise is also important - there are boys and young men out there too who are being misled into thinking that transition is answer to their problems.