Kant rebukes Hume with "Critique of Pure Reason" (Knowledge can be obtained independent of experience) -> Hegel says Kant is too abstract, tries to tie things like morality to social institutions (Family, civil society, state) prone to emphasising freedom -> Marx agrees in part, but says said systems are in fact used as a tool to oppress by those at the top of society for material reasons and maintain inequality ergo things are designed in that way -> Lippman (1922) posits reality as a "pseudo-environment" shaped by individual perception I.E. "constructed reality" -> Critical theorists apply this logic alongside Marxism to the whole of society and posit all institutions, knowledge, language is potentially a tool used to perpetuate some form of oppression -> Post-structuralists argue there are no fixed, universal meetings and everything is influenced by language, context, and power dynamics -> Critical theories posit artificial, oppressive reasons behind everything, and critical queer theory posits that non-heterosexual orientations are suppressed and erased from society wherever and whenever possible, even subconsciously.
Happening concurrently:
Germans begin to posit psychology should be a science and not philosophy thanks to Franz Brentano -> Havelock Ellis (knew Marx's daughter btw) grandfather of sexology creates the terms "autoeroticism" and "narcissism", contributing to Freud's theory of developmental sexuality (also used as the basis for autogynephilia so it evens out) -> Sigmund Freud, inspired by Nietzsche (intuitive thoughts = some latent, hidden knowledge within ourselves) and building on the work of Ellis, develops his theories which posit sexual development begins at infancy and not puberty -> sexology now posits sexual development begins and continues to evolve starting from infancy -> John Money, sexologist, beside creating the term "sexual orientation" (because "preference" implies choice, which he said was not decided by the individual) conducted a human experiment on David Reimer to assert "gender" (another term he insisted on) was the result of societal/social factors I.E. enforced upon the individual by society at large (you already know the rest).
They can't explain it because it's not proven by biology, or science, it's essentially metaphysical philosophical gobbledygook born from the unholy fusion of Marxist-derived culture critique and the more philosophical than scientific fields of psychology/sexology. They can only argue trans people haven't existed in the numbers they do now because society was oppressing them beforehand due to "heteronormativity" and other drivel.