I wasn't one of them, I can't think of anything less fun than sitting on a crowded beach and I have beautiful walking country close to home, but what they did seemed to be within the rules. They were told they could travel as much as they like and be outdoors anywhere, as long as 2m apart. It would be unusual to sit closer than 2m from a stranger, even on a busy beach.
Other people seemed so cross with them, but they were only doing what they were told was OK, so be cross with government, if you must. However, if there hasn't been a related spike, doesn't that prove that there was absolutely nothing wrong with the trips or the advice?
If it had caused a problem over BH weekend, wouldn't we be seeing a big increase in hospital admissions/deaths by now?
And if we aren't doesn't that mean mass outdoor events might be OK to go ahead?