Despite the lessons learned from the Salem Witch Trials, we have seen the damage of mass hysteria repeated. Why do societies throughout history continue to react irrationally in times of fear or panic?
The inability of humans to process what they view as potential fears is what causes irrational fears which have led to situations of mass hysteria, such as in the Salem Witch Trials. Being able to understand what you fear removes much of the fear factor from the thing itself - humans are not scared of the flu, but we are scared of sharks. Although shark attacks happen a lot less frequently than people getting the flu, our inability to understand the process of a shark attack or simply the shark accentuates the original fear we have of the shark.
The same logic applies with problems which cause mass hysteria. Of course, were humans to think rationally, we would be able to pinpoint moments in history similar to situations of fear or panic and realise the best course of action for that given moment in time. However, such situations which cause fear or panic rely on the entity causing the fear or panic to be unrelatable - strange movements and mutterings, for example. For humans, therefore, it is more natural to begin to become hysteric in such situations than to calm down and understand what is occurring, as we do not understand the situation.
Jumping back to the shark example, a life-long shark biologist would not be as fearful of a shark attack as a regular person would be, as the biologist would understand the shark as a organism and an idea more.
https://www.theatlantic.com/health/archive/2014/10/the-psychology-of-irrational-fear/382080/
