Quite frankly, Google has had plenty of time to be working on a Maps application for iOS. It's not like they have to reinvent the wheel with this, they have iOS development teams and experience with mobile mapping applications.
I think that Google willfully chose not to have a product ready. It's a good explanation when you realize they had months of lead time, and when you factor in all of the CEO "I don't know nothing' about no app" comments.