It's OK to not know "why".

Sometimes the reason needs time to manifest.

And, knowing "why" doesn't always return control to you.

The journey towards revenge or justice may result in a less happy life.

The most beneficial reason to know "why" is to either keep it from happening again (because you don't want it), or to make it happen again (because you want it). Neither has any impact on why it happened in the first case.