“The crash happened about 500 feet from lodging where most of the motorcyclists were staying, Hamanne said.”
Bikers not quite up to speed yet, perhaps waiting for others to leave the B&B, truck slams into the rear of them? Bikers turn in front of the truck, truck loses control and slams into the others down the road?
Combined with the possible difficulties of driving with a long trailer - a series of unfortunate events culminated in a disaster.
Once one collision occurred with that long trailer, hard to say exactly what happened.
So close to the where the motor cylclists were staying, could also have been several cyclists waiting for their turn to join others on the road.
It is hardly worth speculating at this point.
There will be an investigation.