Makes sense to me that people would be more comfortable coming out of their closets if they have friends who have already blazed the way.

There's also the little detail that people tend to cluster based on interests and personality traits in the first place, so I could see many ending up in the same circles even if none of them were out yet.

Friends tend to be similar -- you are the average of your 5 closest friends and that -- it is true that my ADHD diagnosis came about because a friend was diagnosed. We became a friend group in college because we were all outcasts in high school haha. Turns out for a few of us the root cause of the social outcasting was different brain wiring

A lot of the things they described had a "wait that's a symptom??" reaction. I have since suggested to a couple of friends to get checked for ADHD in a similar manner if they seem like they might be struggling with it. Worst case they're now in the mental healthcare system and have access to a therapist who can figure out what they're struggling with

When you find a good place you tell your mates about it

I'm guessing there are three effects there:

• People with shared experiences often cluster together in friend groups. (There are autistic friend groups, yet you'd get laughed out of the village for saying “Sally caught autism off her friends”.)

• People tend to come out around people it's safe to come out around.

• Seeing your friends coming out as [whatever] might make you properly consider whether you might also like guys, or Minecraft, or not being a woman.

And they're the same effects in anyone with a socially-frowned-upon interest. Think of the tabletop-RPG-playing “nerds” of yore.