How the hell does one motorcyclist directly rear-end another motorcyclist at high speed in this situation? What is even happening?

Alright, so I see that the first motorcyclist is following pretty closely to some cars, but with a big enough gap for the car filming to pull out behind. The cars in front of the bike slam on the brakes, and I’m guessing the second motorcyclist reacted late to the camera car pulling out, swerved, and somehow also didn’t see that traffic had stopped ahead?

And.. didn’t brake, at all?

And.. didn’t swerve, at all?

And then hits the first motorcyclist, sending the storage box flying into the rider’s head and knocking his helmet off, before flying impossibly high into the air.

At first I thought it was the poor dude’s helmet headed for the atmosphere, but it’s the storage box that goes flying. Well, both, kind of.

Seeing the guy get up and stumble like that is worrisome—he did just literally have a motorcycle rammed up his backside—but I’m more concerned about the reflexes on the other rider who somehow perfectly failed to do anything to avoid this accident.

What the hell?