There are articles written about protective factors that help even very young children deal with trauma. One of the most crucial ones is having emotional support. Another is having a healthy attachment to at least one caregiver. Its almost certain there are genetic factors too since our genes are the foundation of everything related to our physical being, including our brain.
There are likely so many variables it would be hard to pinpoint specific factors. It might be easier to think of commonalities in people who do develop dissociative disorders.