So one of last years soay lambs died last night

it seemed very sudden.
We went to bring them in for the night and she was lying and wouldn't move, she was weak and had a pooey backend. We carried her in and she stood very still with her front feet close together, looking very ill, her jaw seemed to have swollen up. We called the vet, he came and found she had a small prolapse which we hadn't noticed before. He put it back, gave her painkillers and antibiotics and we left her separate from the others.
The vets verdict was that the ram had caused some damage by serving her, yet we hadn't noticed any interest in her, and could she have been in season now? Could it be that some internal infection had made her smell different (hormones) or something? The ewes had been bullying her a little the day before and the ram was seen by a friend pawing at her and butting her whilst she lay ill. I didn't know rams could damage sheep in that way? Is there another illness it could have been?