As I mentioned in another response, there are troubled children who really don’t know. But you would be surprised at the number who know from an early age and will not be dissuaded. A good example is Nicole Maine. Amy Nutt wrote a biography about her, which is well written. She is currently a TV star on the CW’s Supergirl, where she is the main character. The point is that the process takes years to complete. People who are “lying “even if unintentionally, eventually grow out of their delusion. A good example is one of Brad Pitt’s and Angelina Jolie’s daughters, who thought she was transmasc when she was 16. After a couple of years of therapy, she realized she was just trying to deal with finding her way in life and was actually a cis gender girl. She is back to being female. No one makes a decision precipitously. If it is a whim or a delusion, it becomes apparent over time, and the person reverts to their true gender identity.

I do spend time on Twitter, and most of what I see there is nonsense pushed by people with agendas. Since Elon Musk has bought the company, the problem has become even worse. Many of the people posting these tweets are writing fiction to promote an agenda and mislead the public. Now that the fact checkers are mostly gone, there is little filtering of the truth anymore.