I'd bet it was a combination of the "Bird" hitting Angry Birds searches and icon suggesting it was an angry birds game, mario themed art enticing nintendo fans.

I'd bet it was a combination of the "Bird" hitting Angry Birds searches and icon suggesting it was an angry birds game, mario themed art enticing nintendo fans. You often see scam apps employ similar strategies(similar name and icon to popular app, misleading screenshots). The fact that it wasn't a scam, but a playable and potentially interesting game(if you've never played it's predecessors) helped, reviews helped, and the overexcited media eager to report on the next app fad sealed the deal.