This is a topic on which I have dedicated a lot of research and surprisingly there is not much useful information published about this topic on the Internet.
I do think visitors per sales count matters, if you are listing in Fixed-Price listings and suppose you have 10 quantity of a given product. If suppose it takes 200 visitors to trigger one sale compared to your competitor who is selling a similar product but his listing takes only 100 visitors to trigger a sale, common sense says eBay will place his listings above yours because he is giving eBay more business than you are. eBay is a business and they want to earn themselves FVF ( profit ).
Next, I believe your eBay listings title will also determine the listing position, if It has non relevant keywords which are not searched often, those keywords will get the listing pushed down - So chose your keywords wisely and only use relevant keywords to the product. ( You can search through a listing with high sales and see how it is structured and try to be close to them ).
Having a top-rated sellers title will put you infront of someone without a title, basically because eBay knows you have good DSRs and customers are happy with your service as a reward eBay will give a boost to your listings. So customers are exposed to offerings from good sellers on record.
I assume something has to do with the watcher/sales/visitor count aswell, having more watchers on your listings is good but do not go around getting fake watchers who won't turn to potential buyers because that will just pull you down on the search, in conclusion, try to make your listings as complete as possible have 12-pictures, write a clear cut description, use all the category features for instance if you are selling a trouser - mention it's features in the feature section completely do not delete, because some eBay buyers search using the left hand menu of features.
These are some of the reasons, there maybe many more reasons in the eBay algorithm to get to this calculation of who is placed where. To avoid this problem I have almost completely stopped using Fixed Listings, I rely on 3-day auctions a lot of them - because at the ending hours it is placed on the top of search result so it's a benefit.
I am curious to hear more about this topic from the Expert eBay sellers on this forum.