There's no such thing as "the top Google result", Google's search algorithms don't serve up the same results for every search for everyone at every time.

My search results were what I'd expect:

http://i.imgur.com/o9gPJ4c.png

They still don't include the root. Your results are exactly the same as I get, and resolve to these URLs (in order):

https://stackoverflow.com/tour/documentation

https://stackoverflow.com/documentation/documentation/topics

https://stackoverflow.com/documentation/python/topics

None of these are https://stackoverflow.com/documentation .