get visitors from google without any backlinks

FROM MY CASE studies i have found that
you get a low amount of visitors from google in any high competition niche
you just right a post with title in high compition niches and you will get a low amount of visitors from google without one backlink
i need an explanation for this ?
and is there a method for earning counting on this little amount of visitors ?
if i run an amazon review site i guess some of these visitors will buy products through your site
only by writing unique content and alot of posts lets keep it simple

you probably rank for some long tail KW
or on high search volume people are looking many pages and you may also get some clicks on pos 110 or so. (many kw trackers dont go over 100 .. so you think you dont rank but you are maybe 101)