A domain name has very little weight with regards to SERP positioning. They may be using the words that are hyphenated in their domain name as anchor text on IBLs. However, they could have any domain name and use the anchor text that applies to a specific search term. In other words, the domain name is not the reason for their SERP position. It is possible that Google, if that's where you are searching, has picked up this as a new site and all that's in the Google data base is the URL. This would leave nothing to index, however, that effect is very short lived.
Domain names are for humans. Hyphenated names are difficult for humans to remember to include the hyphen. About the only effect they have in
SEO are negative, if there are too many and the domain name looks like spam-spam-spam-spam.com.