Trans and nonbinary people have existed for as long as humanity has. Your perception of this “stupidity” as new is the result of people finally overcoming hundreds of years of religious programming; bigotry that has been passed down for generations as superstitious fear anyone presenting in an unfamiliar way, and people are now more willing to express themselves as they actually feel, rather than as they feel they must in order to protect themselves.

Here’s a short piece of a lecture by a Stanford professor explaining how wrong you are. https://youtu.be/8QScpDGqwsQ