stuckgear
I've no knowledge or expertise regarding aviation in general or flying displays in particular and certainly nothing to offer regarding what went wrong with the Hunter crash that resulted in several dozen people killed and maimed.
But it is not simply an accident. It's not just legal mumbo-jumbo to distinquish between various types of activities and the degree of risk inherent in and/or assumed by those who participate or choose (paying or not) to gather and watch as opposed to those who are uninvolved but get killed or injured without assuming any risk.
To stay away from this event. A person killed in a car accident is dead, no matter whether the driver was drunk, or speeding, or in a poorly maintained vehicle or one that ran off the road and killed a child playing in a schoolyard. The liability varies especially if it it determined that negligence or recklessness were involved. More relevant, at least for this discussion, is that any changes to rules or safeguards arising out of the analysis should reflect greater care for different populations. So, the rules and constraints intended to protect participants or spectators are different from those designed to safeguard others who assumed no specific risk related to the activity. To suggest that the killed motorists who assumed the (perhaps statistically-greater) risk of driving on a public highway therefore also assumed the risk of being incinerated or crushed by a jet aircraft engaged in a spectacle seems a stretch.
Willfully assuming the risk of an accident by engaging in an activity doesn't -- for legal or remedial purposes -- mean assuming all risks from any type of accident.
If that's not what you were implying, then apologies in advance.