There is usually no answer to the big "why" questions. What would an answer do? Clearly it would be some solution that would make all this okay. But can you imagine any answer that would make it all okay? I can't.
That's what makes some problems a real challenge: they call on us to move ahead and reclaim our own lives even though we don't have the answers we want for what has happened in the past. That's also why survivors get advised all the time to spend as little time as possible in the past. We can learn from the past, sure, but the past leaves a lot unanswered. If we keep looking back there for those non-existent answers we will spin our wheels in the past forever.
Nobody living can ever stop me
As I go walking my freedom highway.
Nobody living can make me turn back:
This land was made for you and me. (Woody Guthrie)