WoW was indeed an accident. Not even Blizzard knew it was going to become such a cashcow. Maybe there's only room for one mmo.
They knew it was going to be bigger than everquest, the game they based pretty much everything on. Practicaly "Everquest 2" really. Just they wanted to get rid of some of the dumbass stuff Verant did back then.
What they did not realise is how many people though everquest was a cool idea but coulnd't/woulnd't play it. WoW plugged that hole - the only MMO to do so. Even the real EQ2 was a terribad game at the start, and the new producer imediatly started copying design from WoW.
It was no accident that WoW is the biggest western MMO - its irrelevant what the developers though. It had the publicity and reputation (Blizzard + Warcraft). It had a virgin market (everquest 1 peaked at like 500k and SOE held an event at one point saying they had 1 MILLION players 'pass through' EQ...).
That made it a million seller, blowing its competitor out of the water.
That gave them the ability to make the game into the best MMO ever made (IMO there). I played EQ2 for like two years while WoW was simmering. There are 3 features I prefer in EQ2 (one of them is housing which WoW dosn't even do).
You can't replicate that, which seems to be the problem. AoC had a huge amount of interest but it sucked, and it remains to suck.
WoW got lucky but it was no accident that it got lucky, it was not 'random chance' like the drops are.