some interesting possible causes, this from a self proclaimed autogynphile on this excellent thread https://www.reddit.com/r/GenderCriticalGuys/comments/hhcs34/autogynephilic_male_here_big_rant_about_denial_of/

"a_wild_AGP_appeared 10 days ago

insert 'not an expert' disclaimer here

You're right about the Hippocratic Oath. Back in the 1950s, American doctors refused to perform 'sex changes' (as they were called back then) due to their oaths to do no harm. Patients like George William (Christine) Jorgensen had to travel to Europe to get the surgeries they craved.

Harry Benjamin was the man--a kind and compassionate man by all accounts--who persuaded the US medical establishment to allow surgery to alleviate gender dysphoria. He saw how miserable his patients were, and no cure seemed to exist. He said, "If we cannot alter the conviction to fit the body, should we not alter the body to fit the conviction?"

Essentially, hormones and surgery and living in the desired gender role was palliative care because nothing else worked.

My understanding is that from the 50s until at least the 90s, approval for transitioning was strictly controlled and involved long 'test' periods lasting years, with lots of hoops to jump through, as well as therapy to weed out the people who didn't really need treatment. This is often called the 'gatekeeper' approach. It was resented by many people, who were deeply unhappy due to dysphoria and wanted to transition RIGHT NOW DAMMIT.

Also, the ideal TIM from the gatekeepers' perspective was the HSTS type. AGPs had to pretend to be like HSTS in order to get approval. "No sir, definitely not attracted to women, sir!" And admitting to any kind of sexual motive for transitioning generally got you kicked out. Autogynephilic men like myself learned to downplay or conceal any hint of arousal. It's stayed that way ever since.

Over many years, pressure from the trans activists gradually lowered the barriers to entry and the gatekeepers stopped making such a fuss about whether you were feminine enough, or were attracted to men or women. Which seemed fair at the time. 'Transsexuals' were supposedly much rarer than homosexuals, anyway. Why not make life easier for them?

The trouble is--we're now learning--trans people aren't a fixed percentage of the population like left-handers or homosexuals. Trans is something you become, not something you are. And there are several possible reasons to go trans.

Homosexuals have remained at a steady percentage of the population throughout modern history all over the world: 2-4% of men, 1-2% of women according to the Kinsey Institute (although estimates vary). There's a natural limit to the amount of activist pressure gay, lesbian and bisexual people can exert, because there just aren't that many of them compared to straight people.

And presumably, the number of homosexuals who end up HSTS gradually decreased--at least until very recently--because it became more and more acceptable to live as a feminine gay man rather than a TIM.

But the number of autogynephilic men who were originally given treatment were only a small fraction of the AGP men out there (3% of the male population, maybe more). Recipe for eventual disaster...

At first the gatekeepers were too strict for most of us to bother trying to transition. But the easier it became to get treatment, the more of us opted for it, and the bigger and more powerful the trans lobby grew. Which meant that the barriers dropped even faster since we could exert more and more pressure through sheer numbers.

And a lot of us are white and middle-class--often married with kids and savings (well, kids or savings) by the time we transition--so we have the $$$ and the influence to get what we want from the medical establishment.

At any rate, that's my best guess as to how this has snowballed so quickly.

There are definitely other factors, like LGB organisations jumping onto transgender as the next big worthy cause.

The floodgates appear to have opened in 2013, when the Diagnostic and Statistical Manual revised its criteria for gender dysphoria (previously gender identity disorder) and made it much easier to qualify for medical transition.

... As for narcissistic types and other disorders--I do think it's possible that some people are getting swept up in the trans craze because it's trendy and cool. But that's much more of a problem on the female (TIF) side."