Put yourself in Nikon A&P head's shoes for a second. You spend your budget sponsoring a show and you allow other cameras on the show with the free publicity for them, very soon you will be looking for a job elsewhere right?
Anyway, the objective is very simple, shoe the world that any photographer can use the range of cameras from Nikon to produce very good if not world class images and if another brand's user wins, can state that "Well our cameras are so user friendly that almost anyone can master them." Easiest way to gain publicity with the money spent, don;t you think?