The thing about autists thinking the world runs according to a pre written script that only they got a copy of is broadly accurate from my experience. Though, troons are unusually lacking in self awareness even by autist standards. Still, autists tend to develop what I would call "programmer brain" where they think that interacting with other human beings is about performing a certain set of inputs in order to get a certain output. And they get confused and frustrated when they don't get the output they expect.
Once you know how to spot this, you can see it even in very high functioning autists who are able to lead mostly normal lives, and who aren't socially retarded. If you watch them closely, the way they interact with others can seem weirdly pre rehearsed and unnatural. It's not necessarily that they are psychopaths who don't care for others, but they don't have the same ability to subconsciously "read" people that non autists have. So it takes active effort to not fuck up social situations that most people would be able to navigate without having to really think about what they are doing.
I think one reason why trooning out appeals to autists is that it creates an excuse for being a social retard. Normally, if you can't interact with others properly it's your fault, and you need to learn how to do better. But once you troon out, it is the fault of the rest of the world for being "transphobic", you no longer have a duty to do better because the locus of control for your own fuckups has been externalised.