The term "STEM-bro" predates the genAI boom, at least it begun rising in popularity during the Gamergate controversy.

STEM-bros lack the vision of their peers, they mainly see their field as a 9-to-5, as something that pleases their parents more than a trade school. They were those, who pioneered using fandoms and other nerd-groups as a tool to exclude others, usually through utter toxicity. Then the nerds slowly learned from them, who now think they served the purpose of making sure "the thing they're fans of never changes" rather than to protect the status of some bro, who were into some more obscure stuff.

Sure, many jock-types are nice. There's even a stereotype, that gym-bros are the nicest people. However, VeganGains is a well known counterexample of that. Competitive sports are a lot worse than your average bro pumping iron in the gym. And don't get me started on the "failed jocks", especially those who also frequented fandom circles.

(Please do note, that the whole nerd-jock dichotomy is false, one can be both or neither.)