The fact that people had time to grab a bag is either a symptom of a slow evacuation or some people thought the risk or grabbing their bag was worth it, even if it harmed them and others.
Part of the slow evacuation (and daily slow exiting) comes from the fact that the airlines have significantly reduced the space between the seats. I am of the opinion that for safety reasons, there needs to be at least 12” between the front of one seat and the back of the seat in front of it.