Just because one vehicle gives up the right of way doesn't mean the car or bikes in the other lane are at fault. This case might be a bit different, but what if they were doing a normal speed and ended up hitting the suv? By your logic it would still be their fault because another vehicle stopped and let the suv go?
But for the actions of the riders, which could neither be seen nor foreseen by other drivers, no one would have been injured. Their actions predicated the resulting incident and, on their face, their actions were unlawful. See the posted definition.