It's most likely the same person using more than one account to get around Ebay's identical listings policy.
There are certain categories where this happens on extreme levels. I will see 5 listings by the same seller, with the wording of the title changed ever so slightly so that Ebay doesn't automatically detect that it's identical. (Even though it's exactly the same item) Then, I'll see the same 5 identical listings from 5-10 different sellers. It makes selling in these categories impossible because nobody will ever see your listing among the mass of identical listings.
These are usually sellers in China from what I've seen.