They are very highly rated popular games on Android market and Symbian (we're talking millions of downloads here) so that's probably why they picked them.
Unfortunately, the reason why they are so popular is because they are for low end phones that are prevalent overseas and Amazon users are more tech savvy.
I'm curious as to how you drew that conclusion.
Seems to me using Amazon is a no-brainer(provided one has a western credit card), so easy that even my grandmother could use it. Probably why Amazon has been so successful over the years. I consider myself to be tech savvy, well tech savvy enough to go over the Great Firewall of China and to root Android phones.
However I've had no reason to use Amazon at all, until now.