I accept that he did not intend to cause anyone any difficulty, let alone a shocking and major crash killing several people.
I never said he was guilty of a crime.
All I said was that the cause of the crash was the smoke. It certainly was a main cause (or "root cause").
I accept that drivers contributed to the problem, but none of them would have expected thick black smoke suddenly appearing in a way that suddenly reduced visibility to nothing.
I had a very frightening experience on the M3 a few years ago when I was going at about 75 mph (approx --- ahem! ) and suddenly the light mist turned to a pea-souper and reduced visibility from about 200 yards to about 20 yards.
I was very afraid to stamp on my brakes in case someone behind slammed into me so I slowed down gently. In reality I could have been still hit from behind or I could have found myself slamming into someone in front. I made a guess that as there was no-one in front of me for about 100 yards as I went into the thick fog that I still had about 100 yards to get down to about 15 mph. Luckily it worked out OK for me.