There's more to ranking than just backlinks and keywords. If your site goes viral, get 100,000 views in 2 days, you will temporarily outrank anyone. The niche that I am in has a CPC of $100. You can get an idea of the SEO competition that I might've faced. I wrote this blog post and it goes viral, within the next 15 hours I am up at 5th position for this premium keyword (my DA at that time was 10). This lasted upto 25 days, and went away after that. Initially I thought, well Google fucked up for my good. But, I repeated this experiment, got viral again, my rankings were high. I did this for a year and realized that this leads to short term rankings. Point being, you can overcome ranking barriers, but they are not permanent. Any single page site that ranks for a keyword can be easily outranked with a proper site structure that has a very high topical relevance. Also, these one pagers are called Microsites. I've launched a lot of them, but yes, better be safe than sorry.