I've actually been thinking about this lately. Heres what ive come up with.

The term trolling came from the name of a fishing technique, where you put your bait in the water and then just move your boat around until you get a bite. This is how it started on the internet. Someone would leave some bait in the form of an ignorant comment, and wait for people to reply with angry remarks. Thus, catching the fish.

Then, because people didn't know the term from fishing, they thought it was in reference to the fantasy troll. which makes a little sense, trolls are ugly and stupid, like most trolls on the internet. then the phrase 'don't feed the trolls' came into existence, and continued to reinforce the notion that the reference was towards the fantasy troll. Problem is, fantasy trolls dont really do anything specific, and they vary wildly in different pieces of literature.

Now the term troll has completely changed meanings. any time someone says something slightly annoying, TROLL. playing a prank on someone? HAHA WHAT A TROLL AMIRITE? It's pretty infuriating, but thats how language evolves. It doesn't matter if people use the word the way you think they should, or the way that is technically correct. The word means what the masses make the word mean. So now its just a blanket term for anything funny/stupid/ignorant