This is a great documentary that discusses the advent of using psychology in marketing to manipulate the public. It is not specifically about gender, but it discusses the focus on individual identity expression, which was a marked departure from people's historically group and community focused identities. Basically, advertising gave rise to the market for individual expression and the focus on the self above all else.

A lot of the videos and articles by trans people that are posted here leave me questioning why is the person so self-focused and navel-gazing? But it seems like the logical conclusion of the century of self, identity expression that is so individualistic that it has no basis in material reality and that it becomes cannibalistic, requiring the destruction of the people asserting the identities. And, of course, gender ideology has become one of the greatest marketing successes, taking an illogical, niche idea that goes against everything we know as humans and having it adopted by people and governments around the world, resulting in a growing consumer class that will forever be in need of medical products and services.