Fine for you (and a cool story) but what about the other players - what did they get to do in the meantime?
That's an interesting question. Obviously at the origin story of my PC they got boned, they rolled up new characters. OTOH it was AD&D and it takes 5 minutes, and this stuff happened all the time. I seem to recall that what actually happened is that people lost interest in playing that game, but my friend Mike, the DM, ran all the time, and it was always the same campaign world, so pretty soon we rotated back to D&D and Cargorn joined another party (IE I already had a suitable PC rolled up) and pretty soon Mike baited me with more demogorgon worshipers, and Cargorn got another party killed! Well, then everyone started to think it was amusing, the cursed ranger and all. I don't really recall all what happened after that, but there were tons of games in Mike's campaign, different PCs would mix and match, there were multiple groups of players that only partly overlapped, etc. Every character had their 'thing'. I'd be hard pressed to remember the names and fates of most of the other PCs in those games, but I know some of them became 'big name' characters, some died, some just weren't interesting enough or whatever (I had a doppleganer assassin character, IIRC, which was just pretty vanilla and only ever got to like 8th level).
However, nowadays, with the more 'adventure group focused' kind of play in D&D? I am not sure how exactly that would play out. I expect my obsession with Demogorgon would have led, say in 4e, to that demon lord being somehow significant to epic level play. Maybe killing him was my goal, but getting some artifact he had was another epic PC's goal, etc. Yes, that sort of thing can somewhat run counter to the most low myth kind of play.
@bloodtide is right in this much: the moment a story gets too good to lose, there's a problem. This more commonly arises as a GM issue, frequently leading to railroads and-or trampling of player agency as the GM tries to stick to a "too good" story; but this shows it can be a player-side issue as well.
Meh, I don't know that any trampling happened. It all seemed pretty organic, and it played out over YEARS of real life time through many many sessions of play and was only a major focus now and then. I had an entirely other major character that I often played that had nothing to do with that story arc much at all too.