How did he force his way onto the active roster when he was always on it?
CLG was founded in Season 1 by Jiji and Lilballz, some Taiwanese guys who were just messing around. Jiji got an actual team together consisting of Chauster, Elementz, Kobe24, HSGG and himself, to compete in WCG2010, the first LAN for League of Legends. When they ended up not only winning that, but then proceeding to stomp in a few other small tournaments, they stuck around and did pretty well till Season 1 worlds where they actually only got 5th place, with both TSM and Regi's brother's, Dan's team, EPIK gamer (Dyrus, Dan Dinh, Westrice, Salce, Doublelift was the lineup at the time) outperformed CLG.
Somehow in all of that HSGG got hold of the brand of CLG and became the team owner. Its probably because he ended up financing most of their early expenses through his streaming career, and in general was the most visible member of the team (though Jiji streamed a lot too at the time).
Ever since that performance, CLG has had a LOT of ups and downs (mostly downs), and HSGG was always pressured by either fans or teammates to step down. It wasn't really merited until mid season 2 IMO. What should have happened was HSGG stepped down, Saint and Chauster learn to shot call together, and Voyboy takes over in top lane. What instead happened was Saint got kicked because he was A) a mess (alcoholic... or near to it) B) hated HSGG. HSGG became the jungler. When everyone realized HSGG was an AWFUL jungler, instead of having him step down, put chauster in the jungle, and find a support (Aphro? ... pls not locodoco lol), they kicked Voyboy and put HSGG back in top, Chauster became jungler (beginning the roleswapping meme pretty hard, by this point Chau had played mid/adc/support/jungle for CLG... he'd later play top lane on some wacky lineup they used for online tournaments), and they recruited Locodoco for support.
At IPL5 this fucking travesty of a lineup actually got 5th place, the best of any NA team. Locodoco was fucking awful, fed on everything he played, HSGG was average, just played tanks and didn't feed (meanwhile guys like Caomei and Soaz were doing crazy things with all sorts of picks: nidalee, rengar, khazix, etc).
Season 3 was just kinda... sad. It was obvious by this point HSGG's stubbornness was the reason he was still top lane. Supposedly Doubleift finally told HSGG he would leave the team if he didn't step down, so HSGG did. Of course now that probably is one of the reasons HSGG is so bitter to DL: he was forced to give up his pro career, only to have DL jump ship when CLG finally succeeded.