Only the effect remains

For a team-based game, of course there's the cooperative aspect as a unique selling point. But there's also the fact that sometimes you'll get matched with a good team that carries you, and sometimes you'll personally pull of some really good plays that make for a satisfying match even though you lose overall. There's more potential to feel good even if you aren't playing well, or feel good even if you lose.

I haven't paid too much attention to battle royale games, but the obvious advantage there is that a losing player can tap out early and go on to a new match. If you're doing well you get to ride the high for longer; if you're doing poorly it's over quickly and you get to try again.

"Proper" fighting games are quite a narrow genre—the complex directional inputs, the way characters face each other, the featureless flat arenas, even having two long horizontal health bars at the top of the screen—so it makes sense that there's a shared sense of community, given the degree of transferable knowledge involved.  It makes sense to talk of the FGC in the whole, particularly with the unique culture of in-person 1v1 tournaments.

Well, almost unique.  You've also got Smash Bros, which is clearly outside the narrow genre everyone else is following.  No quarter-circle inputs!  You only win by ring-out!  You have vertical platforms!  You can chuck the enemy off the top of the screen!  It makes sense that there's a divide there, with different language and skills. It really needs to be able to sustain itself to survive.

Yet it's not entirely lacking in overlap either.  More importantly, what else is there to compare to?  Who else is in the business of 1v1 local tournaments?  ...Starcraft 2?