I think there is a level where you are no longer accountable in the way that ordinary people are accountable and I suspect that this is the reason why it happens, but my suspicions are worth absolutely nothing and given that these people are - in spite of the vast amount of information we seem to have about them - so in control of the narratives of their lives that it is impossible to make a diagnosis that will stick. So I will revert to the default: I don't know, but the sample I've seen makes me suspect that there is more to this than just coincidence.