It's not checkmate Scatterbrain. Lhamsuren, who was playing black, decided to follow proper etiqutte and resign rather than play on in a miserable position which would soon be checkmate after 31...Kxh7 32. hxg6 Kxg6 33. Be4 #.

I don't understand how this is checkmate.. Why can't the black king just capture the attacking queen? 

No doubt he did, even if he didn't feel so inside.  From the ratings difference, I suppose he expected to win in any case.  Notice he had the KIA set up by move 6.

I wonder of Fischer managed to appear as cool under pressure - during the match - as it seems from this game.