One of my childhood best friends transitioned and another came out as bi. I think a lot of it is just that people with ADHD and/or on the spectrum tend to get along really well with other ADHD/spectrum people. Since those traits heavily overlap with also being LGBTQ+, those who don’t fall into that overlap end up making friends in their youth with a lot of people who eventually come out later once they figure themselves out.
Man, that is a stretch and a half.
…Which makes it perfect for this community, I suppose