I'm guessing conditioning is a big part of it.
I'd wager the majority or people with more hysterical reactions have lived fairly comfortable lives, without having to face much in the way of dangerous risks. And without that, they also fail to also learn that risks and dangers can be controlled and mitigated. Or that even mild preparedness can mean the difference between recoverable injury and death. So absent this personal experience of a counterpoint to the hysteria on the news, they're more likely to accept prognostications of certain horrible doom uncritically.