“I wanted to write a story that was an allegory or fable about modern capitalist society, something that depicts an extreme competition, somewhat like the extreme competition of life. But I wanted it to use the kind of characters we’ve all met in real life,”
My read of him was that he went back to the games because it was all he knew at that point. I see him more as a tragic character who didn't feel like he could go back to living a normal life after experiencing the games, when no one else would be able to relate or even believe him. At least this way he can confirm that his trauma was real. But the show doesn't really say that so painting him like that might be too generous.