You are right though World of Warcraft and Starwars Galaxies came out around the same time (mid 2003, late-2004).
I should have said Everquest (1999) as that one really started the craze leading to WoW.
But the WoW success is what led the insane MMO bubble/hype as it broke all types of records and everyone wanted to be the next World of Warcraft.
When I worked at Cheyenne Mountain on Stargate Worlds, part of the job was understanding WoW and playing WoW to level 70, then 80 on Wrath of the Lich King, our CEO had done it twice, everyone there played WoW because everyone wanted to replicate it.
Turns out WoW was an outlier not the norm or the future, but every game company wanted subscription money not one and done purchases and it led to tons of investment and hype.
Sony even couldn't replicate Everquest with Everquest 2, Planetside nor Starwars Galaxies, though I loved Planetside.