People are massively overestimating the importance of the main game in regards to OWs success.
Marketing has focused heavily on the characters themselves and many have become attached to them (or at least certain ones) as a result. They’ve already made steps in cashing-in on this influence, they can easily go much further with this.
For an example of this, Pokemon games matter very little for the health of Pokemon as a franchise. The large majority of the revenue comes form merch and rights deals nowadays. People love the universe and the characters often more than the games themselves.