AFAIK, the people on the beach were herded in that manner to allow both Air Ambulances to land near the scene.
I live near Durdle Door (about 30-45 mins or so) and in all the years I've lived in and around this area, I've never once seen the beach as crowded as this news article shows, it's ridiculous. I don't get the mentality of these people. Yesterday, my wife and I discussed going for a walk in the New Forest, which again, isn't too far to drive. When I looked online to find reports of it being really busy, we had a chat and decided it wasn't where we should head to.
Why can't others do the same? It's such an odd thought process 'They're doing it, so I must be allowed', instead of 'That doesn't look very sensible, I'll do something different from those people'...