If you see the games you mentioned, you'll saw the discrepancy of games between those countries: China & South Korean players were top on the PC games competitions, while Japanese players were top on console games.
In console E-Sports competitions, you'll see lots of JP players take part, or even become the top contenders there, like in fighting games (SF/Tekken/DBFZ/etc), Sports (Racing/Soccer), or even shooters (FPS/TPS). Also, in those competitions, you also see only a handful Chinese & South Korean players take part on it (and vice-versa in PC competitions).
This is only a matter of gaming culture stuffs, since Japanese were primarily a console/handheld players, while Chinese & South Korea were more of PC gamers. But this doesn't mean that JP PC gamers were bad. Because there's loads of pro JP players that streams various games everyday like PUBG or Fortnite, but lacks exposure since they streamed on local streaming site like NicoNico or OpenRec, and not on Youtube or Twitch.