I think that it’s partly indoctrination. There’s a reason why every defensive response (for example the younger actors from HP responding to JRK) starts with the mantra, “Trans women are women!”
Beyond that, I suspect there are a lot of young people who believe there is new science to prove it’s true.
A lot of this is not based on knowing and showing the “new discoveries”. Instead it’s based on deliberate undermining of established science, which we know, but don’t tend to prove on an individual or day to day basis.
For example, sex is binary. We all instinctively know that, but as soon as someone claims it’s a spectrum, many would not be able to argue that point. Enough science journals that should know better have bought into this, thus giving it legs.
Ditto the medical profession, which has been so infiltrated that it’s now run politically and not on the evidence.
And recently, there’s been the “challenge” that as we haven’t had our DNA tested, we can’t be sure what it is. The fact that I know mine because I’ve had babies and I know my daughter’s because she went through female puberty and has periods is only convincing if you believe in science and understand that the probabilities are strong enough that testing isn’t essential. My intelligent daughter remains unconvinced as I didn’t respond with sufficient confidence as I wasn’t expecting the question.
I’ve heard over and over that it’s not up for discussion as the science of “trans” is now settled and confirmed.
Many of us believe science we cannot see or prove. Can I prove the Earth isn’t flat? No, I take it on faith that there are scientists who can.
So when the science is deeply undermined, as it has been here, then setting out to prove that first principles about sex and how it works still applies, becomes depressingly difficult. Especially when many people instinctively believe men over women.
We’re not really set up for science. We’ve evolved to have faith. It means that we’re very susceptible when someone with enough standing sets out to deliberately deceive.