Trans people have always existed & did not sneak in through the back door

Trans people have always existed. People who say we didn't exist a few years ago just weren't paying attention. If they say we crept into existence stealthily behind their backs, they're making up a story. They weren't paying attention to the fact that we were always here.

"[Harry] Benjamin's first encounter with trans people took place in the early 1920s, when an MTF spectrum individual" — i.e., a trans woman or a transfeminine person — "sought his help in obtaining female hormones...a request which Benjamin eventually fulfilled...Over the years, Benjamin met with countless trans people, often through referrals from other sexologists..."
— Julia Serano, Whipping Girl, "Chapter 7: Pathological Science," first published 2007, 3rd edition published 2024

Serano goes on to emphasize that transness was not Benjamin's invention.

"In fact, many of the original gatekeepers, including Harry Benjamin, only 'discovered' the existence of transsexuality after trans people approached them about the possibilities of physically transitioning, and many of the earliest transsexuals, such as Christine Jorgensen...and 'Agnes'...self-administered hormones prior to consulting with doctors about their desire to physically transition. Indeed, the gatekeepers didn't 'invent' sex reassignment, but were dragged into it kicking and screaming. And the fact that the gatekeepers almost universally favored strict restrictions that greatly reduced the number of people undergoing sex reassignment clearly indicates that they were, at best, reluctant advocates."

Serano explains that, on the one hand, you can "acknowledge that trans people have existed in varied cultures and throughout history" and "view transsexuality as part of a natural rather than culture-specific phenomenon and thus understand trans people's desire to live in their identified sex as being primarily driven by their own intrinsic inclinations rather than by social forces." Or, like Bernice L. Hausman in her 1995 book Changing Sex, you can "narrowly define transsexuality as the act of changing one's sex via physically transitioning," which makes transsexuality dependent on 20th-century science; analogously, you might say "transportation is a modern construction dependent on the discovery of fossil fuel and combustion engines." And by so "removing transsexuality from this trans-historical and cross-cultural context, Hausman misleads her readers into believing that trans people suddenly appeared out of nowhere, almost overnight — a fabrication that practically strong-arms her readership into seeing transsexuality as a culturally specific and socially derived phenomenon."

While Hausman says homosexuality is different in this regard, Serano points out that it may not be. "After all, both words, 'homosexuality' and 'transsexuality,' were coined within the last 150 years, gained prominence as concepts with the rise of sexology in the twentieth century, and emerged as identities and poiltical movements both because of and in response to their psychological pathologization. And if one were hell-bent on portraying homosexuality as entirely constructed," one could argue that more people are openly gay these days not because of "political and cultural changes" but because "the medical invention of homosexuality itself generated a 'demand' for people to become homosexual." (One should not say this. Serano is just pointing out that Hausman is making a false distinction, applying the model to transsexuality but not to homosexuality.)

Also

"By the 1960s and ’70s, trans folks were already laying the foundations of modern U.S. trans culture. Communication between trans people on their own terms, without interference or filtration from medical institutions, was finally possible; Sylvia Rivera and Marsha P. Johnson founded Street Transvestite Action Revolutionaries (STAR) to help other trans people of color find stable shelter; the first Christopher Street Liberation Day march took place in 1970, eventually leading to the modern concept of a 'Pride parade.'"
— This Archive Offers an Incredible Window Into the Early Trans Internet, Samantha Riedel, them, November 22, 2023

Also

Hil Malatino (Trans Care, 2020) writes that "a common feature of trans arts of cultivating resilience has to do with turning to the historical record for proof of life, for evidence that trans lives are livable because they've been lived."

Ronan Kennedy, July 15, 2023 on Twitter:

"Its 8 years since the #GenderRecognitionAct passed in Ireland and its so interesting to watch people suddenly think it was passed into law by stealth. Even one senator, who is currently very exercised about the whole thing, didn't speak on a single one of the debates."

Learn more about Ireland's Gender Recognition Act 2015.

On the other hand, you will also hear stories that there was a debate over some proposed law or policy, and that "trans activists" — a "mob," that is, two or more trans people — spoke loudly and overran the debate, ensuring that cis people could never be heard. So there's that too.