The process must have gone something like this: Firefly contacts Firaxis, asks nicely to use its Civ franchise name; together they work out a city-based structure using all the familiar aspects of Civ, applicable to cities at any stage of civilisation; they decide on Rome as its historical connotations make it the best place to start the franchise, and they decide on a hands-off city-building structure, as that's the best way to watch all the little people doing their thing. Oh, and they throw in a military section as an afterthought. Now what do they call it?
Um, Caesar IV?
I mean, this is hardly the leap from Sim City to The Sims, where an established franchise branched out into an original, excitingly unexplored area, is it now? This is the much smaller step from one established genre to another, which someone else just happens to be predominant in. And Firefly hasn't chosen the Aztecs or the Babylonians or the Mongols or any of the thousands of other civilisations that have been studiously ignored; they've opted for the heavily-caligae-trodden roads of Rome. Even the map screen, where you trade for goods or send out armed expeditions is a poor imitation of the one from Children of the Nile. I mean, come on Firefly, the people who buy city-building games have seen the competition as well.