They didn't have the resources to go RWD. However, they could and should have used an upgraded version of the AWD chassis from the Magna TJ/TL and made that standard.

I think that making any large car however, whatever drivetrain was used, was doomed to fail. Perhaps Mitsubishi Australia should have investigated manufacturing localised versions of the Pajero, Outlander and the Lancer several years ago. These ranges sell well for Mitsubishi. Their large car hasn't sold well for almost a decade now.