Adding to this summarizing my reading from elsewhere: It sounds as if the cause was going too slowly through a sector, and due to to combination of wet conditions and the specific layout of the sectors at Sepang it was triggered for the first time. Since everyone was driving in formation on the formation lap, multiple drivers triggered it.

Would this be safety-related, something like "going this slowly through a sector indicates a problem, kill the throttle"? Still seems heavy-handed since the cars were moving, if dangerously slowly.