Post hoc ergo propter hoc
I still want to take a better look at that keyword, doesn't seem that competitive. Very competitive kws just don't temporarily jump to almost first page.
I recall early days of DFB/xrumer, I was using it heavily on my money sites and they were ranking like nothing I've ever seen before. Then one day they started disappearing from serps. Not dropping or dancing - disappearing even for their brands.
Needless to say I was scared shitless and blamed xrumer first, but then noticed a strange pattern: subpages were still ranking fine and it was isolated to one hosting account. Everyone dispensed the usual advice: keep building links, unique content, optimize images, keyword density, don't put all your eggs in one basket, if all fails give up and move on, yada yada...
... until I logged into GWT and saw a ton of crawling errors - Googlebot simply couldn't access the sites. Turned out there was an issue with my hosting's firewall that nobody knew about. One email to admin solved the problem and sites were back to #1 spots next day. I could've built all the links I wanted and it wouldn't do shit, sites still seemed offline to G.
Sometimes things aren't what they seem, especially when hundreds of factors are involved such as with SEO.