I just don't get why he passed away.

I've searched the internet for bunny illnesses and he didn't have the symptoms for any. He had no symptoms. He didn't get into anything either. He was just a happy bunny.
I did read about other people losing their bunnies suddenly with no cause to show. They say it just can happen.
I think we are done with bunnies as pets. Too heartbreaking.
Thank you all for your support.