While there may be some truth in the theory that the attack occured because our government was covertly sending Libyan arms to Syria and got caught, that would be one reason for a cover-up. But regardless of the reason for the attack, there is a certain other reason for a cover-up.
Consider that Obama snatched the presidency from Hillary Clinton. Now consider that, to appease the powerful Clintons and to get them to work with Obama, the administration makes a deal with them - they would make Hillary Secretary of State, so that she could build up her resume with some major foreign policy experience so she would have an easy time winning the White House in 2016. Consider, too, that the Democrat party does not have ANYONE who could beat Hillary in 2016.
So what we now have is an administration dedicated to keeping control of America in 2016 by ensuring the election of Clinton.
But Clinton screwed up, BIG time, with Benghazi. She refused to send the support and help that the Ambassador repeatedly requested. She ignored the real threat. And between them, Clinton and Obama were asleep at the wheel when the "call came in at 3:00 am." And our people died.
It would immediately be seen as a devastating blow to both the administration and the Democrat's chances of winning the White House in 2016 if the people got even a hint that Hillary screwed up so badly, and that Obama did nothing to help our people who were under attack.
And almost before the sun arose next morning, Susan Rice was lying on all 5 major morning shows, and since then the administration has done everything in its power to sweep this under the rug. Survivors were threatened into silence. A stupid video no one ever saw was blamed. Lie after lie was invented and trotted out, hoping to "wait out the clock." And the liberal media acted in collusion with the administration, keeping the truth from the people.
We may not be certain as to why the consulate was attacked, but I am 100% certain as to why it was covered up so aggressively.