Upside,
You may never know why or how he was damaged. That is why he is on a mission to find himself. He needs to understand why or how it happened.

I wouldn't sit around pondering this too much as the answers will not come to you because you were not around him at that age. In time, he may reveal some of it to you or your children, but he's just not there yet.

It's time to partially shut the door and look to what you need to do to heal and move on a bit.

Sit quietly, the answers will reveal themselves when you least expect them to.
The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.