Plenty of speculation, but all accounts indicate that the anchor did not fail. The rope that held the guide and the male client was severed. How this happened, I do not have a clear picture of, though I have a couple scenarios that could have occurred.
An assumption of mine, is the guide may have been counter balancing off the male client when rappelling to assist. If the rope was cut above him, but below the anchor, and the male client was leaning back on the opposite end, this could have caused both to fall as the cut rope ran through the master point. This is pure speculation, and only based off what has been reported in the papers.
Perhaps we will find out more when any possible statute of limitations runs out or those involved are out of harms way from litigation.