Cannot figure out how this site ranks so well

Here is the site in question. budgetplumbingonline (dot) com they rank in the top 3 organic positions as well as the local pack for just about every plumber keyword. Looking at (plumbers greenville sc) since it has the highest search volume of that keyword variation. How are they doing this? Their backlink profile is very weak, site is full of technical errors, site is not mobile friendly, content on site isnt very well optimized if at all. The only thing I can find is the site loads very quickly. Am i missing something? Can anyone offer insight into how they rank so well?

Because it's the only website to use the keywords in question? That's what I have observed.

I think its a relatively old site, at 10 years. Maybe it'll start moving down within the next few months. Other sites such as Yelp & YellowPages have authority but lack in content depth.

The age of the domain matters a lot in ranking factors. Maybe that could be the reason the site is ranking up in search engine pages.

Are you sure that you have the right numbers?

I didn't get anything from analyzing their website, there was not enought data.

Perhaps they are only focusing on keywords. But from their footer, it seems that they didn't update their website from 2014.

The other reason might be that they are blocking spiders from semrush like services. So, the data you are seeing is not even relevant. I block almost all popular spy checker tools from my site