Not one person posting on HN and the many blogs really knows what happened behind the scenes. Apple engineers are not known for being dumb. Someone had to know that Maps was a bad idea. A huge step backwards. They had to know.
So the question might very well be: Why did they do it?
This couldn't have been out of spite. Just to kick Google off the platform. One just doesn't do that. Maintaining a complex code-base such as iOS is difficult enough. Adding to that the friction of delivering a substandard product is not something one does without very good reasons.
Conjecture is all we have from the outside. My humble guess is that it had to come down to a business deal they did not want to make. The details of the deal are not important. Who was right and who was wrong isn't important. What is important is that whatever they had in front of them convinced Apple management that it they had no choice but to, effectively, downgrade the next release with Maps.
I already know of a lot of non-tech people, particularly outside the US, who are livid about Maps. After dutifully upgrading their devices to iOS 6 they discover that Maps are, in their words, "crap", "useless", "unreliable", "a joke", "not accurate", "una mierda" (shit), etc. The reason for the strong feelings is that, let's face it, if a good tool such as Google Maps is available to you, you might tend to use it.
And a lot of people would use it all the time. My own wife relies on Google Maps all the time. Thankfully she was wise enough to marry a geek who promptly told her not to upgrade her iPhone 4S to iOS 6 and not to swap it out for an iPhone 5. In fact, not one person in my family will do either of those things. And that is the case --that has to be the case-- for millions of people at this point.
This is the data we are not getting and that Apple will probably never release. I own eight iOS devices. Not one of them will be upgraded to iOS 6. In fact, the upgrades stop here until either Maps starts to get really good marks. And, of course, we probably would have purchased at least three iPhone 5's. Not happening. I'll get one for development but it will not be activated.
How many millions are in this boat? If someone is a heavy Google Maps user it makes no sense to get an iPhone 5. What's wrong with a 4S? Nothing. Use their website you say? Not the same, most would say.
As a developer there's a lesson that needs reinforcing every-so-often. What better way to reinforce it than to see a tech giant make some of the mistakes lesser companies make: If you can at all help it, don't base your product on someone else's technology. Don't make someone else's technology such an important part of your offering that not having them will hurt you. Of course, sometimes you have no choice.
As a user and a developer I view iOS 6 as a significant, if not huge, step backwards. Between Maps and the eviscerated app store one has to ask that cliche-ish question: What were they thinking?
Wouldn't we like to know.