1 year old rabbit died, causes?

Hey everyone. I have a question for anyone who knows a little about rabbits or animals in general.
Over a year ago (October 2021), my rabbit died. He was just under a year old, so I was pretty sure something was wrong with him.

We bought a total of 3 rabbits back then, two females and one male.
Mine was the male and when we bought the rabbits (August 2020), we went to the vet and everything was fine.

Now to the point: My rabbit had hair loss on his rear end and a slight redness (kind of like an infection). We thought maybe he was having a fight with one of the females and she was pulling out his hair, so we ignored it. And two months later, I found him dead with blood pouring from his eye.

Our cage has three compartments and thus also a "staircase." There were some bloodstains on this "staircase," which told me he must have bled quite a bit.

When I checked him out, I noticed that his hair loss was getting worse and that he was only bleeding from his eye.

It wasn't as if he had injured himself in any way since the bleeding was coming from inside the eye and nothing else was visible on his eye.

Even then, I knew something was wrong. But we didn't go to the vet or anything; we just went straight to bury the rabbit.

Anyway, I thought maybe one of you could help me, since his death still weighs on me quite a bit. But maybe knowing why he died will give me some peace. 🙁

LG