Because a decade ago marks when the American right decided to scapegoat transwomen after losing their previous scapegoat, gay people and marriage, to SCOTUS in 2015.
2015-2016 is when rhetoric online and globally shifted towards villainizing trans women that weren't on the public's radar before. This was exported to UK politics and has been an incredible political success.
Yes, because it's a selfish movement and damages acceptance of the rest of us in LGB. We are allowed to criticize it. Have you ever thought, people were tired of people making everything, their whole personalities, etc, about gender and how marginalized they are? Living in one of the most prosperous parts of the world. THAT is why we criticize it.
If that is the cause, how does it explain both the sex ratio shift and the rapid increase in referrals starting from around 2011-2012 onwards? There were gender clinics across Europe reporting similar demographic changes in pediatric referrals. This precedes the political developments in the US that you mentioned.