Hypothesis: The reason that neurodivergent people (esp. autistic people) tend to lean more trans per capita is because a lot of default gender roles, norms, and assumptions are neurotypical assumed. Thus since there is no pre-packaged "space," ND people have to explore their space in the gender-world "manually."
We're willing to bet that if NT people were in a similar space where they were forced to actively examine their gender and not take anything for granted, we'd see similar rates.