What's actually stopping the traffic?
Without watching the "documentary" about this "historic moment," I'd guess that they decided to do this during rush hour when the 405 is basically a parking lot anyway. They got a few cars to stop across a few lanes, Don hopped out, acted like a dumbass, and then ran back to the car giggling about being a "bad ass."
Edit: Watched the "documentary." lol, Don references Tiananmen Square. I'm not sure adding congestion to rush hour traffic to advertise a shoe is in anyway relatable to "Tank Man's" protest or all the students who had been protesting/dying for due process, democracy, freedom of the press, and freedom of speech in China in '89.

This was pretty awesome though: