i think it has to do with a couple of things:
The world is becoming more accepting of trans and alternate gender identities. It's not the best right now, but compared to the 70s, 80s, and 90s today has gotten better.
Also, the internet has been a great catalyst for all people to learn more about transitioning and to be involved in more internet related trans topics. It seems that younger people uses the internet, on average, more than someone...say...in their middle ages.
So I think that has something to do with a larger younger group.