The edgelord thing goes back way further than 4chan and Something Awful. I remember plenty of racist fascist rapist satanic misanthropist kitten smasher edgelords from the BBS days. It was not serious, though sometimes it was I hate my dad and I just got the new NiN album serious.
At some point something did change though. It was around the same time as Gamergate and it’s been written about extensively. I’ve been into edgy hacker adjacent culture since like 1992 and when the “actual not ironic” stuff landed it was immediately recognizable as something unfamiliar and different. I’m still not sure how many people got “pilled” versus how much of it was some kind of weird collision with normie spaces where people didn’t get the culture.
There was a generational shift in there too. OG hacker culture was GenX and older millennials, the people who grew up with the net pre enshittification. The /pol stuff and GG seems like younger millennials and GenZ.
I am not pretending to have a clue and I don’t think anyone truly does. It’s all a very complex soup of memes and people and influences.