In my personal opinion based on my observations. I believe that the people who care are more likely to snap if things don't go the way they planned. Whereas People who don't care, well, they don't care. Thoughts?
I think if it was so easy to determine who was gonna snap based on these factors, we wouldn't have any of these unforeseen violent events in the world. Not on a small or large scale.
I think a lot of factors go into the tendency to snap, and some of them are definitely calculable. But they aren't things like plans that fell through, or people not caring about stuff etc.