Stories about forbidden love have been around for centuries. It’s something that readers, writers, filmmakers, and audiences have been fascinated by ever since. Now, to relate it to students, high school students spend most of their days at school and deal with a lot of hormonal changes and curiosity regarding romance and sexuality, so because of that and the propinquity effect, they’re most likely to find a boyfriend/girlfriend in school than anywhere else.
Spending most of your days in high school + forbidden love + a certain preference for an older romantic partner = teacher-student fantasies.
And the more it’s normalized in the media (like on Episode), the easier it is to normalize it further in people’s minds.
Since this is a thread to just talk about why this trope has been normalized, I hope I don’t have to precise that teacher-student relationships should in no way ever be normalized. Anyway, that was my hypothesis, I hope it made sense