He put a ton into gates, then didn't bother using them. Hell, I don't think there was any point in the game where all of his gates were on cooldown. He even dropped a proxy pylon, and never bothered using it.

Not that it would have ultimately mattered, two-base turtle is not going to hold up for long against an aggressively expanding four base zerg, particularly when he has all but ceded entire map control to the zerg.