Well, it's a chainmail vest--easy enough to add some leather straps on the sides to help it loosen (after all, Chainmail was an armour used in Europe for decades because it was easy enough to just hand down to your children and have them resize it themselves). Not to mention, it was taken by an eldritch being who then regifted it to the orcs. It's possible that through that process it was resized magically.
But I'm actually more partial to the idea that the Orcish rendition of the Legionaire armor was taken by the orcs and mutilated and twisted by their craftsmen to be fitted to them, making it look haggard and rough, perhaps corrupted through their own magic (which I'm aware they likely don't have much of).
But I'm actually more partial to the idea that the Orcish rendition of the Legionaire armor was taken by the orcs and mutilated and twisted by their craftsmen to be fitted to them, making it look haggard and rough, perhaps corrupted through their own magic (which I'm aware they likely don't have much of).