I don’t know if any of those three would suffice. I suspect, given the relatively weak external motivations for authoring IF, most motives are internal.
How about: Your English teacher offered you to create something for his creative writing circle which you could also hand in as coursework to improve your grades, which in turn he would be forced to drastically lower otherwise due to the unfortunate group dynamics you started in his classroom when you couldn’t stop yourself from describing his favourite plot conundrum in his favourite 20th century outsider literature work as “really a very tiresome and transparent construction and weakly written, too.”