It's extremely common for cults to use an existential threat to keep cult members tied to the cult. One of the more famous ones is Scientology and the psychiatrists who are trying to murder everyone always for millions of years to lock their thetans in. For troons it's TERFs, and since an absurd number of them LARP as communists (plus Trump-era rhetoric), fascists.
You're not going to believe The Cis are you? They told you you were a boy and you shouldn't cut off your dick. Of course they're going to tell you nobody wants to kill you. But those of us with experience know better, The Cis want to Genocide trans people constantly because reasons. That's what TERFs and fascists do, they hate and they Genocide. Are you saying they don't want to hate and Genocide you? They told you you were a boy and shouldn't cut off your dick and they hate you for defying them. The Cis don't even understand the euphoria of being trans, they think euphoria is morally wrong and what do you do with things that are morally wrong? You eliminate them. And since they hate and they're fascists they want to eliminate trans people through Genocide, the worst of all crimes. You were just an egg so you didn't experience what we have with this constant threat attacking us.
I think the troon cult is a little bit unique in that they mostly seem to be convincing each other of this rather than it being imposed deliberately from the cult leaders. Even in the case I used of Scientology where L. Ron Hubbard actually believed that shit about psychiatry it was because he was saying it that the rest were to believe. It's not like there's some single or even a cabal of troon leaders who had the power to decide this, it seems like they all just amped each other up trying to top each others rhetoric: misgendering is transphobic -> forms of transphobia, like misgendering, is violence -> transphobes want to do literal violence -> transphobes want to genocide all trans people -> transphobes are currently doing Literal Genocide.
It's one of those unanswerable questions as to how many of them truly believe this stuff, how many are just performing it because everyone else does and how many are just doing it because it's useful or they think it will be useful to get what they want since other people are things to be manipulated. It's probably a mix. It's not like they can deny it and deviate from the group. That's internalized transphobia and helps assist the TERFs and fascists to Genocide everyone.