The odds of being in a plane crash today 52.6 million:1, so when you hear that you’ve missed a flight that crashed with no survivors, you’re going to be pretty overcome with emotion. top that off with the fact that she and her husband were the only people who didnt board the plane, they’re gonna be suffering PTSD.
My theory is after the learned what happened, they were so overwhelmed that couldn’t function normally and crashed in the car. Or perhaps more sinister is they decided to put fate in their own hands and kill themselves.
Auto accidents are extremely common – your chance of dying as the result of a car crash is something like 30 to 1. Additional mitigating factors, as you suggest, make it even more likely.
The odds of missing a doomed flight doesn’t play into the equation, since it had already happened. (A common logic mistake.)
I don’t think a theory is necessary at all, as MVA fatalities are fairly common. I don’t have the stats for Italy, but in the United States over 34,000 people died in automobile accidents in the year 2014 alone. In the previous years the number was around 40,000 deaths per year.
Per the National Safety Council, the odds of dying in a motor vehicle incident of any kind are 1 in 112. The odds of dying as an occupant of an automobile are 1 in 492. Dying in a air or space transport incident is 1 in 8,357. This particular chart does not break out “passenger in a commercial airliner”.