TL;DW…
Basically WayForward had built a working relationship with Nintendo over the past 8 or so years, and they would meet with the big N at every E3 as WayForward came prepared with different pitches. Finally when it came time for Nintendo to revive Advance Wars, they went to WayForward pretty much right away.
Source is above: the Fragments of Silicon podcast.
by Asad_Farooqui