I blame sci-fi. As a kid in 90s who was into this stuff, it seemed like anyone who knew about dark matter knew it was just theorized and never observed. It was

I blame sci-fi. As a kid in 90s who was into this stuff, it seemed like anyone who knew about dark matter knew it was just theorized and never observed. It was included as a caveat in a lot of things I read to ensure the readers understood this. Then in sci-fi it started showing up as a material the characters would interact with, and a lot more people were introduced to the term. Then as a teen in the 2000s the caveat was usually gone and it started being treated as something we had proof of. People I knew started thinking it was something we'd actually found and was now fact instead of theory.