What's to understand?Al Quaida is a named enemy of the United States in the statutes authorizing the WOT in 2001.
Al Quaida is one of the enemies of the Assad regime in Syria.
Chris Stevens was recovering Ghadaffi's weapons in Libya, thence to supply "rebels" in Syria via Turkey, rebels that include Al Quaida.
Therefore the administration was providing aid to an enemy per the Constitutional standards for capital treason.
Whether to off the guy who knew, or if the whole thing blew up in their faces, either way they needed a cover story. Hence the video.
Hence all the leftist smoke defending the President against an investigation of Benghazi as a GOP political stunt.