Welcome to the Q&A Forum

Just because your site has more links, a higher domain authority, and other competitive factors does not mean you will out rank other sites in search engines. What you should do is a on page analysis of your competitor, for the page that they out rank you for in the SERP, and then do the same for you page that shows below theirs. Compare the two, and see who has the better grade. It sounds as though they have better on page SEO for that Key word. If the results come back the same then they are a lot of other factors that could be causing them to rank above you. Like better off page SEO or a lower bounce rate.