Well everyone is stating the obvious
The thing that got me the most was the piss poor response to the downed cyclist who took the primary impact
This guy should have been kept on the ground and as immobile as possible, he should have been checked for obvious broken bones and other "at risk" injuries as well as being monitored for shock.
He should have been protected as much as possible from being hit again by other traffic, by placing a vehicle between him and approaching traffic, or whatever other means- such as people doing traffic control to divert traffic around the accident scene.
He was obviously the one who needed the most attention, the motorcyclist had ATGATT [full protective riding gear] and the second cyclist took less of the impact.
Yes everybody, we all need to learn not to "target fixate" [I'm guilty of doing it too]........
But PLEASE do a certified first aid course, preferably a "Level 2" or whatever your local equivalent is, there are also motorcyclist specific first aid courses available in many cases.
Not only can it help save the life of one of your riding buddies, it may also save your child/wife/parent/best mate, or maybe even someone you don't know that is loved by someone else who will be grateful to you for being capable of making a difference.
I'm Level 2 certified as a work requirement and my wife and I both did a motorcyclist specific certified course as well three years ago [time for her to do an update].