Yeah that Roman armor was only for aesthetic and craftsmanship, the muscle look wasn't supposed to be intimidating on those, that had more to do with the Romans and the Greeks being obsessed with the look of the human body, then you see the armors of the knights, they all have funny shapes and no fake muscles, then there's the Samurai armors, they don't have fake muscles, just plates on top of plates, you know what they have? Ugly masks, those masks were supposed to be intimidating.
So I disagree, the "muscle look" does not come from there, comics didn't start with the muscle look until the late 80's, before that costumes looked like just really tight tights but still looked like clothing, then with the boom for body builders, bodies in comics started getting drawn more and more extreme and someone had the fantastic idea that the fabric on those costumes should stick to every individual fiber of muscle despite the body types being drawn became increasingly more unrealistic to the point of being ridiculous, and that trend caught on, why? To impress 14 year olds at the time, it was purely a stylistic choice, then movie makers started having problems recreating the comicbook look, problems that didn't have in the time of Christopher Reeve, so they came up with the idea of fake rubber muscles, and that's where it came from, it didn't come from those Roman armors.
Story and all that has nothing to do with, it's just the representation of a very specific style of art, nothing more. The armor look is slowly taking over the muscle look, characters like Cap are no longer wearing tights in the comics, they're wearing armor, the new Batman is literally an armored mech, the real Batman is currently "dead" but I wouldn't be surprised if the new design when he comes back is more armor oriented.