Hi!
It can be a great many things that casues the rankings to be different. Perhaps some of these are fitting to your site:
- Your site gives a better experience than your competitors on mobile
- Your site has a greater CTR from organic search results than your competitors
- (Mobile) page speed
- Font setup on mobile vs dekstop (readability and user experience)
I found this article on SearchEngingWatch that could be of interest to you.
Best regards,
Anders