It’s no accident that historically the appearance of an idea of “trans” (sexual or gender or anything else), from first around the 1930s onwards but mainly from the 1950s, is completely coextensive with two things:
- women’s legal rights; and
- the development of modern surgery/antibiotics.
Pretty much all instances of “trans” people that gender ideologists lay a claim to that were documented before 1900 were actually homosexual men and women, living at a time when sexual orientation was understood as inseparable from sex and sex roles, and wanting to be the other sex was thought of as evidence of homosexuality, not “gender dysphoria”. Gay and autogynephilic men might have played at dressing up in women’s clothes; but there was no appeal to “living as a woman” in eras where that meant a very severe loss of autonomy, money, agency and legal rights.
“Transsexual”, as something rooted in a desire for surgical alterations of the body, also did not exist as anything other than pure fantasy before the era of modern surgery and antibiotics. It’s almost impossible for us to think ourselves back into a time where routine, safe surgery didn’t exist. Surgery was minimal, noninvasive or only in extremis before modern medicine (and, crucially, antibiotics), made infection and complications generally rare.
People might have fantasised about turning themselves into the opposite sex - Joyce has Leopold Bloom do this in a satirical section on Havelock Ellis and Kraft-Ebing in Ulysses - but it remained a fantasy, because complex body-altering plastic surgery simply did not exist then. They weren’t “trans” in the contemporary sense, because the idea of being one “gender” trapped in a different sex also simply didn’t exist. People might even have wished quite hard that they had been born the opposite sex: but until very recently in history this wish was on the level of any other impossible wish — like; I wish I had been born tall, or rich, or possessed of great beauty or good fortune — ie. it remained merely a desire/fantasy.
It would have made as much sense to someone in 1820 to say that a man was “really” a woman trapped in a man’s body, as to say that the King secretly thought he was spiritually a pauper trapped in the body of a monarch; or that Adam Smith thought he was a Frenchman trapped in the body of a Scot.
The reason you don’t see actual historical evidence of “trans people always having been there” is that for most of history it simply didn’t register as an idea that was any more than merely fantastical or metaphorical. Aside from gay men, a very few lesbian women, and women who didn’t much like their social role as chattels, there isn’t much of any evidence in history of “trans” anything at all.