Speaking from experience investigating accidents, it is extremely rare for any car accident not to be the fault of one of the drivers. Even in cases of sudden mechanical failure, that is usually down to deferred maintenance, the manner of driving, or ignoring warning lights io the dashboard. Sudden ill health is no excuse either. With the exception of a sudden massive heart attack, which generally happens after warning symptoms that have gone unrecognised, a vehicle can normally be brought to a controlled stop for help to be sought.
Misjudging speed or the severity of a bend is probably the number one cause of single vehicle accidents. Bears a remarkable similarity to the events at Shoreham, just in a vertical axis. (I was going to say plane, but that might have come across rather flippantly).
Looking back through my records, there isn't a single accident that I dealt with where blame could not be placed firmly on one or more of the drivers involved.