One of the glaring issues with transgenderism is the total lack of logic. It's a piece of piss to pull it apart in one or two questions.
So there are a lot of people who aren't doing it to expose the sexism, or support women, but who do it to make the, albeit satisfying, point that it's incoherent nonsense.
It does expose the sexism, but only if you're looking.
Notice how these men don't talk to transmen and complain that they are appropriating manhood?
Because they don't give a fuck. As transmen's appropriation of manhood is barely noticeable by men because it has no power.