I can tell you that the lack of brands selling the product may be related to a Patent (potentially). If NOT, then I personally would not worry about how many brands are dominating unless you know for a fact that they are getting sales by pushing traffic to Amazon from something else (TV ads, famous brand, Infomercial, etc…).
Ice scrapers in 2015 were dominated by the brand Mallory in the United States. ALL but one listing on page 1 was a Mallory product. I decided to sell against that brand, and I was able to do so very easily. The main reason was because it was all just resellers selling their products wholesale, and they don’t care about Amazon sales as a brand necessarily.
Also, neither myself nor anyone I knew could name a single “ice scraper brand” on OR off of Amazon. So, it became pretty clear to me that this brand just happened to be FIRST to market as opposed to BEST to market.
What do you think about your situation? Is it “they just happened to be there before you?” Or is it “they are truly really good and hard to compete with?”