his motivation isn't mentioned in the commentary during that clip, but the structure of that show was that the "loose cannon" (i.e., the casual player selected by pokerstars to appear with the "pros") who came away the biggest winner in the season won - in addition to the money he won on the show - a prize package valued at $50k consisting of buy-ins and expenses to attend various live tournaments. this guy was leading at the time he played with a $140k profit, so he wanted to lock it up and get the prize package as well.
He's a math teacher at ASU too! Some of my friends knew him. Unfortunately that douche Bobby "The Bus" Ferdinand, a well-known and very disliked Foxwoods regular, ended up getting it in with AA vs. KK in the last few hands to take the profit lead and the NAPT passport. If you dig in on him a little you can find out that he went broke quickly and his fiancee', whom he planned on marrying after the show, left him. There's all kinds of stories about Bobby out there like him throwing chips at other players and tearing up cards at the table.
Fishman vs. Hellmuth.
Also worth noting that they're playing Jose Rjio poker, where it's pot-limit pre-flop, and no-limit after the flop, so he can't jam all in. If he could jam, it's an easy move to pick up a few grand, because everyone would know exactly what he has.
I believe he had also played another premium hand to the flop after the hand vs. Hellmuth (and before the aces) and was totally lost as to what to do, which likely informed his decision.
This was by far the best poker show on TV, for all these extra dynamics. Sad it's not on anymore.