Single Page Websites

Hi

I currently work in the gambling affiliate industry and I'm new to the whole SEO side of things however i have noticed that there are quite a few one page site who rank highly for certain key words.

I've looked over the site and read the content and can't quite understand how they're doing it? I've run back link tests on each of the sites and nothing comes up so they haven't been building any links.

Would someone be able to help me understand how they do it as this seems like quite a simple way to generate traffic to the page?

Thanks

I've seen one pagers ranking on the first page to, only for low competition long tail keywords though. what are you using to lookup back links? Maybe they've used a PBN?

They may be chose low competition keywords or they may be promotes their sites by social media

I've seen crap sites with almost zero backlinks on first page for medium competition keywords (non english) and for me to get there I have to write tons of content and spend money on sape links, but apparently my competitors are getting there for free, weird.

Most likely they use PBNs and hide their backlinks.