i tried to find the origin of the word after I saw that

I'm too old man.

for reference, the first use of it was Stan, the insane fan who murders his girlfriend and wife to get attention from his hero, in the Eminem song. I think he picked the name based on "biggest fan" rhyming with "this is Stan" - picking names because they rhyme is a signature part of his style

and via that it became part of hip-hop culture (Nas made a diss track where he referred to his opponent as a Stan)

it became a common insult in hip-hop, emerged via ohnotheydidnt as a way to make fun of obsessive fans outside of the hip-hop community specifically,

and now it's just its own thing

I didn't realize that was Devon Sawa!