He's not trying to win the debate, he's doing it for exposure. It's fairly likely that he has a new venture planned in the near future, and he wants his brand in the public sphere. This is an incredibly low risk opportunity for him, as he can't lose the debate such that it would negatively affect his future viewership. He's likely calculated that now is a prime time to launch something as his BNTSG viewership is now at an age where they would like something new in that sphere.
I doubt it. He's been doing this for a while now, I think it's just his current vocation, arguing with climate change deniers or creationists. When he's not doing c list celebrity appearances or "Dancing With the Stars" or whathaveyou. Rarely possible to be overly cynical of public figure's motivations, though, so you may be right.
To make a long story short, I don't take any responsibility for anything I post here. It's not news, it's not truth, it's not serious. It's parody. It's satire. It's bitter. It's angsty. Your mother's a *****. You like to jack off dogs. That's right, you heard me. You like to grab that dog by the bone and rub it like a ski pole. Your dad? ***. Your priest? Straight. **** off and let me post. It's not true, it's all in good fun. Now go away.