Whereditgo
Journeyman Pro
20 cars circulating at reduced speeds, but still well over 100 mph. Just saw some stats from Canada. Under normal conditions, F1 cars took the speed trap before Turn 13 at over 188 mph. Under the safety car, they took the speed trap at "only" 160 mph. So, put yourself in the position of a race martial, who may be clearing large parts of a track of debris, or in a vulnerable position repairing a barrier or removing a car. You have up to 20 cars randomly driving past at well over 100 mph. I wouldn't fancy it.
As Beedee said, bunching the cars together is purely about safety. It leaves large windows where marshals will know the track will be clear of F1 cars. Safety is the only reason the safety car will be out in the first place. It will often be seen as the last resort (well, before red flagging the race anyway). So, bunching the field is absolutely not an intended consequence to simply wipe out a large gap between cars. If it was intended, then the safety car would be brought out much more often.
This is the benefit of the Virtual Safety Car, where these gaps remain in place. This is the preferred option over the full Safety Car, but will only be chosen if it is considered safe.
I'm not suggesting the cars (less than 20, because at least one has been involved in the incident, in fact I think there were substantially less than 20 still on track?) circulate at the speeds you are stating, I originally suggested the pit lane speed limiter be employed, but agreed that would be too slow. The cars are also able to slow further if necessary as they approach and pass the incident. You seem to be suggesting that the 160 mph behind the safety car is a safer speed? Whilst I get that the safety of marshalls and drivers is paramount, the safety car too often affects the result.
Personally I think the race directors statement of "we went racing" indicates that he thought he was doing the right thing by trying to get the race finished under a green flag, but that was a mistake.