the Toss player tried to wall in the zerg player with a proxy build
a proxy build is where you build your base not at your base, but someplace else closer to the action
with the wall in place, he was able to keep the zerg player from expanding, something the zerg really want
what happens next is really awesome, the zerg player creates a tunnel to the other guys base, which has 0 defenses, just in time to get the shit out of dodge while the Toss player is moving in
they base trade and the zerg player has 2 units that the Toss player cant attack, thus making him the eventual winner
the zerg player essentially did everything right in order to win, despite looking like he was fucked the entire game.