Allahpundit thinks it's clear:
The White House had plenty of reason to suspect more was going on than a protest that got out of hand, even from the very beginning. But that would meddle with one of O’s strongest reelection narratives, i.e. the president who demolished Al Qaeda (read this for a stark illustration of how certain key supporters are helping him out with that), so we didn’t hear about it until Eli Lake and CNN and Reuters all but dragged it out of him. What we didn’t know until now is that the White House Situation Room got a heads up on whodunnit early enough that Chris Stevens may well have still been alive at the time.
In the same story that breaks the news and gives readers the e-mails, CBS News prints an unaired answer that Obama gave Steve Kroft on September 12. It was his first interview after the attacks. "You're right that this is not a situation that was — exactly the same as what happened in Egypt and my suspicion is that there are folks involved in this who were looking to target Americans from the start."
Weigel places the blame elsewhere:
Obama didn't pretend that this was merely "a protest that got out of hand." The trouble, when we look back at the timeline, is that reporters didn't really glom onto the Libya story for a few days. When they did, by the Sunday shows and September 19, you had administration spokespeople soft-peddling the "target Americans from the start" story. Before that, though, if you followed the story, you knew that Ansar al-Sharia took credit for the attacks, and that Obama was calling them "acts of terror."