It really confused me too, my guess is that with so much money on the line it amplifies any emotions you feel by so much more. Maybe it was the lack of respect of the other players, or maybe it was just him realizing how much money he was going to win and was happy about it? Much more noble than Friedman, at any rate...

I think that the guy whose wife got cancer and the armless guy almost started crying too...but it's totally understandable in their cases. Andrew Black starting up was just out of nowhere.