If it was a "Without Sony this game wouldn't exist" situation, I doubt there would be a PC version ala Deep Down.
Something comes to mind on this- Sony money-hatted Injustice Ultimate Edition, yet a PC version was still released. This seems to be the same.
Fighting game players were mostly on 360 last generation since PSN is a piece of shit in regards to netcode for fighters and a lot of the buyers are playing online. (Tournament players bought 360 because that's where most of the tournaments were played so they weren't "frame lagged," as well)
That's not quite the reason why. The Capcom fighters run better on 360, so the majority of tournament players all play on it over PS3. The PS3 versions of the games are like .1 frames off compared to the arcade versions of SFIV, IIRC. Some small number that nobody else would ever notice. Online play has nothing to do with it-- to hardcore players, netcode is shit no matter what the game and platform is.

There are also some games where the community is on one platform over the other
just because, like Tekken players sticking to Sony consoles.
It's not hard to see Sony buying it to get the fanbase on one system and not compete over frames/"arcade perfect" etc for tournaments.
That said, I can't see it being a huge "get" for Sony in regards to getting more than... 2million max (and that's being generous) on the system.
This is definitely huge for the fighting game community. Sony has "won" in that sense, but like you said it really doesn't matter. I would argue that fighting game players were going to shift over to PS4 anyway, since stuff like GG are only on Sony platforms anyway.