I have a 1994 Isuzu Rodeo, my title also says Isuzu
Rodeo. But why is my front grill a Honda Passport,
it is the original grill...
The early Passports were made by Isuzu. It's a rebranded Rodeo. Honda literally paid Isuzu to slap some Honda badges on their Rodeos so Honda could get into the SUV market. So most (if not all) parts swap. My guess is your Rodeo lost it's grille and someone replaced it with a Honda grille just because it fit. It would not have left the factory with a Honda grille, gone to a dealership, and been sold with a Honda grille in place. So someone at some point put it there.