Why is it that extrovert types end up being introverted after traumatic episodes? Because the trauma pushes them into their introverted shadow.
The reason people go through cognitive transitions from one side of their mind to another is to solve problems that the current side of their mind can’t. Extroverts transition to their introverted shadow to deal with pain as a coping mechanism. It’s like a hedgehog rolling into a ball when it’s in danger - they shift their outward focus inward as a survival mechanism to protect their ego.
If they are continuously experiencing trauma, and thus spending a lot of time in their shadow (which takes a lot of mental energy), the brain will try to re-establish an energy equilibrium by growing new neuronal connections to more efficiently use the shadow cognitive functions. This is how a person becomes Unconscious Developed (UD).