It always makes me laugh with MMOs, they think people are going to leave WoW to play a half arsed microtransaction addled clone of it and are surprised when their shit tier attempt fails. The last time any creativity in MMOs happened it was Star Wars Galaxies until they tried to turn that to into WoW, which suffice to say was about was popular as a terminal disease.
This has changed a bit, but that's due to the number of potential players increasing.
There's room in the industry and market for two big boys of a distinct enough genre going at a time when it comes to games that require a high time investment. So that's two MMOs, two mass market FPS, two open world single player games, two live service open world games, and two grindy looters. This is especially so if they have distinct enough genre settings. Open world single player games cycle faster, about 6 months with a bonus month every DLC, everyone else gets a year from release, with MMO expansions resetting the clock. Anything breaking these rules is an outlier. That's why March and November are the battle ground months for AAA releases. Everyone is hoping to claim their slot for the cycle.
About 10 years ago there was only enough market share for one per genre, which is why the sway between Call of Duty and Battlefield used to be more intense. That's part of why WoW was unassailable for so long, FF14 Realm Reborn basically only arrived right as there was enough room for two. If it was too early it'd have died as well. At current growth another slot is due around 2030. Until then you need to be able to kill either WoW or FF14 to be a big MMO on the market.
This also applies in F2P games. There can only be two big ones in a genre at a time. For example: DoTA and League of Legends. Warframe and Path of Exile.
This rule also exists for shorter single player games, but those have a way longer tail on people buying them and being able to justify it, as well you see longer term profits go further, meaning once launch development costs are covered the game becomes perpetual money if it is good. As even if launch window is crowded if they get good press people will cycle through a bunch of them before the following March/November flood.