I argue somewhat otherwise. Rome was always more of an agriculturally based society unlike the Phonecians, Carthaginians, Greeks, Trojans and others more tactically based upon the coastlines of their regions. Ever notice that these coastal empires were much more loosely based, smaller, stretched thinly than when compared to larger sedentary empires?
Rome came on the scene much later than Phenecians, Carthaginians, Greeks and Trojans. Some claim Romans descended from Trojans. The Empire that drove the center of Phonecian world from east Mediterrenean to Carthage was the Persian Empire. The various thalassocracy appeared "loosely based, smaller, stretched thinly" because they all had very small population. The very fact that they were "empires" at all was because their sea-born trade system was generating far greater wealth for them than farming would, especially on their own poor soil. It's like saying Brits had a very thinly spread empire compared to Russians and Chinese, but if the 10 million or so Brits circa 1800 had been on a continent, they would have been nobodies.
They occupy what could be seen as one half of the nomadic demographic in world population living under the notions of travel and migration based on ship travel instead of riding on horse despite apparently having conducted themselves inside city walls. Even the Greeks who were supposedly a great sea peoples ended up controlling a less than decent portion of land, patchwork comes to mind
Many Greek states started off with very poor and broken land to begin with. That's why some of the city states took to the seaborne trade. And through seaborne trade, at the peak of its power, Athens was controlling practically all the agricultural output of the Black Sea coast, the bread basket of Europe at that time.
The patchwork was what allowed various Greek city states to try their own things and find out what works . . . instead of say a Spartan Emperor enforcing a sea ban on the rest of Greece, as a way of protecting the price of agro products from Pelopennese.
until it was Alexander that gave them a truly solid empire. But Alexander was from Macedonia and being further inland thought differently about empire.
Alexander's universal empire lasted only a few years. There were only a dozen years from his becoming king of Macedonia to his death, when his empire fell apart. Not sure why that's called "truly solid empire." Although Alexander himself strived to leave his Greek subjects alone and not debase them with "oriental despotism" which his newly conquered Persia was bringing him, his universal empire did eventually bring to Greece the "oriental despotic" influences that Athens and Sparta fought so hard and succeeded against a couple hundred years earlier.
Sea empire usually deal with trade and their network are tactical to seeking trends of income and ways of surviving away from predatory outsiders that they are rarely made aware of larger ambitions away from the piecemeal dominance of the coastlines.
Yes, it's called profit motives and doing the sensible thing. Land empires do tend to suffer from megalomania more often. On rare occasions that might actually succeed temporarily, but most aspiring "kings of the world" inland never got anywhere despite drenching their subjects in rivers of blood. Some deep inland nomads seem to be afflicted even worse with this megalomania. When one only looks at the "successful" ones, the study would suffer from data point selection bias.
It was no terrific feat that Rome could conquer all these comparatively small and defenseless places. Even the Punic wars were fought by underdeveloped Roman ships against a water savvy people of the Carthaginians and the Romans still won.
Carthage was not defenseless. It had dominated the west Med for some 500 years before finally being vanquished by Rome, all while having a very small population (partly due to its child-sacrificing religion); it was founded by a small band of refugees from Phonecia only around 800BC on a small patch of "leased" land. Carthage lost the 1st Punic War because some dingbats in the Carthage senate decided to disband the navy in order to expand the empire inland in Africa (perhaps to get more farm land?). That's the most important among the three Punic wars, as that defeat meant Rome would be in control of the sea lines of communication in subsequent wars.