It's pretty obvious to me that the Walmart Wonder sold better than they expected, and they wanted to make it widely available.
They waited until they could do it in alignment with Apple’s brand, going back to Steve Jobs saying during the netbook hysteria: “We don’t know how to build a sub-$500 computer that is not a piece of junk. [1]”
And to their credit the Mac Neo is not a piece of junk.
[1]: https:http://bits.blogs.nytimes.com/2008/10/21/blogs/21bits-read-m...