“How did the attackers know in advance that Stevens was going to be there on that day when nobody else did?”
Hmmm....
“...the details of his visit to Benghazi, where he and his staff died, were meant to be confidential.”
http://www.independent.co.uk/news/world/politics/revealed-inside-story-of-us-envoys-assassination-8135797.html
The fact that the attack was coordinated with the protest in Egypt and the number of people involved in the attack and the way it was carried out, it took more than just a couple of days of planning and training and something done on the fly. It took planning and training over a period of time to carry this out.
That's why they keep talking about the video as the trigger and try making it sound as it was spontaneous and not planned.
Hillary sent him there.