I still don't get how the collective Greek-culture nation failed. When did this happen? I would have guessed 1941, but they specifically stated 'Ancient'. 146, 64 and 30 BC seem likely, but that's on the barest edge of 'Ancient'.
But looking to the most traditional and most Greek city of all, we can find a link. When Sparta broke with tradition and freed the helots in the 3rd C BC, did that help them? No, they paid dearly. And became Romans.
I don't know, maybe I'm over-analysing it but I found the single thread of logical thought and I followed it to its conclusion, damn it.
The idea that The Romans and the Greeks somehow collapsed in the way a modern state would collapse is a deep misunderstanding of the ancient world.
First, one must understand that the concept of Nation and the Concept of State are separate concepts. A Nation is all the people who label themselves the same thing. A State is a government body and the land it controls, and the inhabitants of that land. The Nation-State is a fairly recently established one, in which all nations of peoples ought to have a state for themselves to dwell in.
While there was certainly a Greek nation for centuries, there were many Greek States, at least until Macedon conquered the Peninsula. When Macedon under Alexander conquered Persia to the Indus river, they did not somehow displace all the peoples living there and replace them with greeks. The State is a very tenuous thing in this period, and has far more to do with where the cities ship their tax tribute to, and whose face is on the coins, than anything else.
The greeks never turned their backs on their traditional values; they differed from city to city in very divergent and incompatible ways. Consider the Tyranny of the Thirty, when Sparta conquered Athens and installed a despotic ruling class of 30 men, restricted voting rights to a highly select elite group, and stripped rights away from lower classes. It ended in violent rebellion of course.
The Romans on the other hand are another matter entirely. Though we like to look at maps with pretty boarders showing the extent of the Roman Empire covering everything from England to North Africa, Spain to Syria, the simple fact is that anything recognizably Roman was mostly absent beyond the Italian peninsula. There were colonial settlements of course, cultural assimilation throughout the Empire, but most of it's territory consisted of nations of other peoples that simply submitted to Roman overlordship, lest they be conquered by force, or peoples conquered by force and forcefully held under the Roman Eagle's wing. In addition, the Romans habitually welcomed nations from outside their borders into the empire as Federated peoples. They allied with Rome, and were given land to settle in.
While the reasons for the Western collapse are poorly understood, and far too complex to ever be really analyzed, the final breaking point simply must have been that the Western Empire simply no longer had the power to assert it's authority and project it's power to enforce it's laws and borders. The emperor had no clothes, as they say. Thus, the people who were already there simply became independent of the Empire, and other Imperial land was gobbled up by Scandinavian invaders who met only the most token resistance.
The Eastern Empire on the other hand remained able to enforce it's laws and borders, and lingered longer. Though, I do suppose they abandoned their traditional principles. The Romans adopted Christianity after centuries of Paganism. Somehow, I doubt that's the intended message of the commercial though.