Probably based on observations made of the player. Since he was raising JT, his preflop range is obviously real wide and Helmuth I'm sure took note of that. A 3bet would likely just illicit a fold, since the preflop raiser's range is weak. A case is definitely there for just shipping in preflop, since 22k is a pretty solid portion of Helmuth's stack, so just sticking that on isn't a bad result. Instead Helmuth chose to flat the 22k, making the pot 44k (ended up being more) against someone who seems to have a LAGy image.
Villain should fire at least a cbet a majority of the time, at which point Helmuth can jam drawy boards for about $100k on top, denying most draws correct odds
, or on a dry board he could perhaps flat a flop cbet and jam the turn if villain 2barrels.
Instead he called, the pot got bloated to over 100k, he had about that left in his stack, and there's no way you're folding AA with an SPR of 1.
He was probably thinking something like that.