I'm not familiar with the discovery in question, but I do find it fascinating. I would think that the reason it's so surprising is mostly because of how counter-evolution it is. The theory of natural selection posits that specimens with better genes will pass them down, as they tend to survive longer than those with faulty genes.
This means that every generation in a genetically diverse environment will have the combined genes of two genetically superior specimens. Inbreeding tends to lead to bad genetics, because the lack of diversity means that superior mutations rarely of ever enter the gene pool.
That's what makes this discovery so unique-- For whatever reason, those Mouflon are entirely inbred, and yet their genes are strong anyway. That might make a huge impact on how we think of evolution.
Hope this answers your question, haha sorry it's so long-winded <3