a) in my experience, most people don’t know about the flash, what it can do and what it can’t. These people are those you can see taking pictures with flash in great sport events. I guess that these kind of people don’t really know how to work the flash on their cameras

b) many consumer cameras have fancy red-eye-reduction pre-flight or pre-flashes. The actual flash for the exposure comes seconds after hitting the button. This is not really productive for a “La Ola” (audience wave)…

c) The trigger to flash seems to have been one guy running along the bridge. This is too slow to be impressive on a long-distance shot.