What if the Athenian Sicilian Campaign , 415 -- 413 B.C. , had been successful, during the Peloponnesian War?

There were two great and devastating disasters that are particularly credited for Athens' loss to Sparta during the great Peloponnesian War, 431-404 B.C. The first was the Great Plague of Athens, striking just one year into the war, that wiped out 25% of the population of Athens. The second was Athens' devastating defeat during the Sicilian Campaign, some fifteen years later. The purpose of this extremely ambitious campaign was, apparently, to establish an overwhelming and invincible Athenian overseas empire stretching over perhaps a thousand miles of land and sea, and the control of the extremely rich land of Sicily, and the great city of Syracuse. In principle, control of all of this territory might have made Athens virtually invincible, and might even have led, eventually, to Athenian control over the city of Carthage, and the Carthaginian Empire. Given this level of power, would Rome have ever even have arisen to become a great power? Would we have the prospect of a Greater Athens stretching over most of Eurasia, larger even than Alexander's Empire? How durable could such an Empire have been, given the nature of Athenian democracy? The campaign itself was crushed, eventually, with massive loss of men, ships and military power, and it was this defeat that clearly led to the ultimate defeat of Athens some ten years later. Nevertheless, it's by no means clear that the Athenians couldn't have won. They won many battles, and took much territory. So, let's suppose they did succeed in taking full control of Sicily. What happens, historically?