I wonder if there is a strange middle ground, where bad actors cling on to something as a belief at the most basic level - even when they don't really believe it - because it's the only way they can justify who they are to themselves.
I'll try and explain myself better.
The thought first occurred to me when I watched the BBC Jimmy Savile drama (it's excellent) with Steve Coogan. The jarring disconnect between Savile's very unchristian actions and his desperate need for validation from the priest during confession was fascinating. He was sharing some of his dark thoughts with the priest but also desperate to hear that god was there for him. Obviously it's very possibly just artistic licence but it gave some food for thought.
When someone has dark thoughts (such as a paraphilia, or multiple paraphilias - Savile's multiple ones and how this changed over time are explored in the drama, albeit briefly) they are unlikely to want to think of themselves as unpalatable to the world. Obviously they don't care about what others think on some level and most of what they probably care about is feeding their narcissism and/or nefarious desires. But deep down, I should imagine everyone has the need to be at peace with themselves, otherwise you're completely rudderless and wouldn't be able to pass off as "normal" at a societal level. We all anchor onto our own core values and hold ourselves to those standards. Sometimes this incorporates outside beliefs or crosses over with them (I'm an atheist but I used to believe in god and some of my core values trace back to those days).
I'm no psychologist but I'm guessing there's some form of self-gaslighting that kicks in. To the point where everything is "ok" if you can centre it on your feigned belief. Maybe then your feigned belief starts to feel more "real". You know you're faking what you're saying and doing - going through the motions - but you're so well practised at it that you internalise enough of it as true.
I wonder if it might help someone to reconcile how someone can know their behaviour is not remotely Christian but they can still trot out all of the Christian things that people are meant to say. And be completely at peace with this disconnect. Or in the case of gender identity belief, they know that when undeniable facts are thrown at it (e.g it is undeniable that sex and gender identity are not the same thing - and that this means one is a physical reality and the other is something you carry in your head as a concept) they can concede it but then the flip switch kicks in and they are back to trotting out all of the things that those who truly believe in gender identity would say.
So eventually what they actually believe and what they pretend to believe get a bit muddled up. Nothing is ever real for them but they can anchor on to it just enough to function and seem "normal" when actually, their paraphilia(s) never really switches off and they are always planning how to indulge it or already secretly doing so (possibly while hiding in plain sight).
If someone gets a high enough profile, they don't even have to care if most of what they say doesn't make any cohesive sense, to anyone else or to themselves. Or if it's never the same as what they said previously. It's all totally fluid, allowing them to sound "reasonable" and "engaged" in the moment.