I want to apologise in advance if I bring up shit that has been discussed ad nauseam because I frankly lack the time, the autism and the stamina to go through 88 pages of troonposting. I'll mainly just address OP's question.
How do people become trannies? Disregarding some extreme fringe cases like individuals being forced into it, North American men legally changing their gender to cheese the feminist system or Iranian homosexuals trooning out to avoid the death penalty for being gay, I've noticed three main origin stories.
1. Gender dysphoria
When basically your brain chemistry is all fucked up to the point you feel trapped into the wrong gender's body. Some really extreme cases can result into that one guy Josh did a stream on who felt he was a pad (which he stopped after getting HRT). Gender dysphoria can, especially among young children, be treated through psycho- and hormone therapy. If gone untreated to a certain age, it's too late.
2. Untreated trauma
Which I believe should be self-explanatory. Similar to how paedophiles and
some homosexuals are made, being a victim of emotional, sexual or other physical abuse, especially during your childhood, can fuck you up to the point you become a tranny. Similarly to gender dysphoria, the damages done here can be fixed, or at the very least band-aided, through competent and professional psychotherapy.
3. Escapism
Basically when your life is at the tail end of a downward spiral you see trooning out as a possible salvation. When you're plagued by a myriad of issues like for example being morbidly obese, an addict, short, ugly, an incel/femcel or having little to no self-esteem to speak of or being otherwise maladjusted to the point of getting disgusted by your own body and you lack the strength, the will and the support network to improve your situation, you'll see getting under the knife as an increasingly tempting option. However shitty your situation may be, it gets even amplified if you have autism. This is for example my hypothesis on why Jim Sterling and Digipaedo trooned out. After the initial euphoria of escaping into your "new" body and "new" life as fizzles out, you will get brutally hit by the realisation that whatever problems you had, could have possibly all been solved, except for the problem that you irreparably mutilated your body and threw your hormone system out of whack. Just like a person who jumps off a bridge and realises that all their problems could have been solved except for the fact that they just jumped off a bridge. The thought process of trooning out as a form of escape is eerily similar to suicide. And speaking of which, this is where the 41% come from. Personally I believe that the overwhelming majority of trannies fall under this category.
Of course those categories aren't mutually exclusive and do often overlap, especially 2. and 3..
Discuss the validity of transgender ideology here.
From a scientific standpoint there is hardly any validity to speak of. The biological reality is that in order to change your sex, like for example the protagonist in
Ranma ½, you'd have to do it on a genetic level, for which medical technology is, as I'm writing this, not sophisticated enough yet. Maybe one day if you could transplant your brain into a cyborg body that looks like the opposite sex, though that would open a different set of can of worms.
How valid is it socio-politically? I'd say it has proven both its validity and viability as a political movement beyond any reasonable doubt. As I said in other threads, political troonism is how feminism monkey pawed itself. Whatever arguments you may have for why women should have the same rights as men, are the
exact same arguments trannies use for why they should be treated like women. The system that feminists have established that lets women LARP as men at the expense of men, is now being used by men to LARP as women at the expense of women. And the results speak for themselves. Trannies have politically been lately gathering Ws left and right to the point where feminism - for the first time in its history in the western civilised world - has been getting BTFO'd and steamrolled mercilessly. In every legal and political fight between women and trannies, the trannies will almost always win because in a zeitgeist that values equality above everything else, the system has no choice but to side with the trannies. As a result you have trannies in female sports, showers, bathrooms, prison etc. Trannies are also undermining and hijacking women's issues and rights. And on top of that, the (North American) lesbian community has now been all but completely subverted and overtaken by trannies to the point where lesbian women are now shamed into having sex with troons. In other words, trannies have achieved what MRAs and the political right could only dream of.
Politically troonism is a massive success story. Individually it's nothing but a tragedy.
That's my entire take on the trans question. Sorry for the wall of 'tism and assburgers.