In terms of money the FGC has nothing on the likes of DOTA 2, CS:GO and those major esports though for prize pools, sponsors and the like. Outside of the Capcom Pro Tour, and when WB\Neverrealm pump money into the scene for their latest Fighting game, you don’t currently play games like Tekken to make a comfortable living. Even the profitability of the games isn’t on the same level as Overwatch, CS:GO and the like.
The FGC has a lot going for it when it comes to having a sizable dedicated, rusted on fanbase and other things but the first winner of Fortnite’s esports made more money in one game than currently even the best FGC player could hope to make in a single season of playing tournaments and sponsorships.