The brain processes and integrates emotional/instinctive responses, not abstract concepts -- even in situations where said responses are themselves caused by abstract triggers (e.g. stock market crash and subsequent loss of wealth/job/etc.).

In fact, the reason why some people are more resilient to the effects of PTSD than others is already well understood:

"While the presence or absence of any of these responses are not necessarily predictive, people who take a more active, problem-solving approach to the traumatic event are less likely to develop PTSD, while those who dissociate are more likely to develop PTSD."

https://www.voa.org/understanding-ptsd