1) Search for "Google Maps" and it is the 5th result. The app is literally called Google Maps. The results before: Fine Maps, PD Maps Worldwide Edition, Google Earth(?!).
2) 300 comments and the topic of Apple anti-competitive behaviour with regard to App availability is hardly touched. In fact the top most comments are on UI and nitpicking over details such as Bookmarks and response speed.
I suspect that this is simply due to some part of the searching algorithm that takes things like number of downloads and publishing date into account. Over time the position will probably change.
I suspect (And this is entirely speculation on my part) that if iOS Maps had not been under such a cloud of scrutiny since it launched, we might not have seen Google Maps.
With so many having major issues with iOS Maps, and Apple needing to do a lot of catch up, being seen to block a reasonable solution would be very, very bad. Especially the same week as the well publicized "Sending people into the middle of the Australian outback with no mobile reception instead of the city they put in" news on iOS Maps.
Not trying to sound conspiracy theorist here, but observing past behaviours and the likely influence of current demands.
And anti-competitive maybe a bit strong. But wasn't it Google Voice that has been stranded in review for a while now?
I think Apple's mono-culture is beginning to fail: using the App Store as a gateway to their devices (touched on briefly above), etc.