Cosmic:
I’m not so certain these type of accidents are caused by tail-gating. They are more likely to be caused by a HGV hitting stationary traffic due to the driver not paying attention.
Probably a bit of both in reality. Any truck driver that follows another truck too close has no idea about what is happening on the road ahead and the inevitable happens.
Also many drivers don’t allow for the unexpected which happens from time to time and again the inevitable happens.