How are people getting millions of backlinks?

So many competitors in my industries have literally 10000+ backlinks from websites that barely exist or clearly just exist to feed backlinks, I even found that one of these companies had backlinks on a porn site. I know for a fact that their webmasters aren't reaching out to these insanely obscure websites and freaking porn sites for backlinks. Can anyone explain how they are doing this??? The game feels rigged and I'm getting really frustrated.