May the departed souls rest in peace.
The major factor for such accidents at night is due to the driver falling asleep. Its happened before and this could be a typical case of such a case.
The other two factors could be a tire blowout (which cant be the case unless the left rear tire was the culprit) or confronting an animal due to which a sudden swerve of the steering could be disastrous.
I notice so many cars tailgating on the motorway. They will just come right behind you and go crazy with flashers and horns. Very hazardous and dangerous.