SF is the bigger game with more money in play. VF is niche as fuck and he wouldn't get paid to travel and compete internationally with it. The only reason people know him is because he won an EVO back in the day, and he probably realized he could do more with SF than he ever could with VF. Good on him to concentrate on the game more likely to bankroll his hobby.
I doubt he ever stopped playing VF tho. The last time VF showed up at Evo (2012?) Sega hosted a tournament where he kicked all of our asses while also competing in SF4 and SFxT. He's a machine that will play anything.
I'm pretty sure he stopped playing it on the regular when Sega stopped doing their Star Player program, which was in 2014 or so? (Sega has been sponsoring players in VF for the better part of 20 years -- it's crazy how ahead of the curve they were with this). He did come to the US for Sega Cup 2013 and 2014 and took everyone's money then, so he was still actively playing then.
I actually got to play him at Sega Cup 2013 and I got
bodied. Even playing someone like Itabashi Zangief, it at least felt like I could try to do things and make adjustments (even if I got outplayed most of the time), but playing Fuudo felt like playing a robot specifically designed to just crush people's existences in videogames.
Moral of this story: He's freakishly good in a number of games in a way almost no one else is. Don't forget his multiple national titles in Gunslinger Stratos or his Kaidan rank in Beatmania IIDX.