[Benji]

Idra said on Inside the game that he left because he thought the CC being built at the gold was a 4th (saw the 3rd CC in base and thought it was at the west gold when in reality MMA killed it, something Idra could never even consider), and given that income, expected another wave of Marine/Medivac/Tank to be heading to the middle to reestablish that position, which he had no way to counter production wise, combined with the drop at the natural which he couldn't clean up fast enough.