This is a classic difference of perceptions.
Flight deck and cabin crew have been taught from day one to view flying from one perspective while passengers have been brainwashed by the airlines to view flying from an entirely different one. When something goes wrong and shocks passengers from this dream, the result is what we see here.
Flight deck and cabin crew know that flying, while very safe, is fraught with potential dangers, and have been trained to deal with them. In the unlikely event that something unusual does happen, they hopefully have the presence of mind to deal with it as they have been trained to.
Passengers have been lulled by airlines into thinking that flying isn't much different from sitting in their living rooms. You have music, video, magazines, food, etc. to distract you from the fact that you're hurtling through space in a metal tube. The upper classes can get downright luxurious. The airlines really don't want them to be thinking about anything that might go wrong. Safety briefings are often perfunctory, saying just enough to satisfy the FARs. And for 99.99% of the time, this is sufficient. When something does go wrong, is it any wonder that passengers are totally unprepared to deal with it? They likely have no idea what to expect, no way to assess the level of danger, no experience with processing all the sensations they are encountering. They are frightened, in shock, adrenalin pumping, and each individual reacts to this differently. How could anyone expect rational thought from them. They feel helpless and are completely at the mercy of the crew, who they look to for guidance.
Telling passengers to pay attention to the safety briefing isn't going to help much. Nothing can prepare passengers for what they will actually experience if they haven't been through it before. Pity the poor passengers on that recent Quantas flight. Why should they be expected to experience anything other than absolute fear when without warning their peaceful flight is suddenly interrupted by complete pandemonium? Other than perhaps a few, who among them should be expected to maintain the presence of mind to do exactly as they were told during the three-minute briefing that occurred hours earlier. All they are thinking about at that moment is the sudden realization of their mortality and that they are, in fact, hurtling through the air at a great height with tremendous speed in a flimsy metal tube.