Ive recently been reading up on my Second Macedonian wars up until the fall of the Seleucid empire, and how Rome was able to dominate and absorb the numerous Hellenic Kingdoms and leagues. The question I've been wondering is exactly how the notoriously snooty Greeks reacted to Rome prior to conquest and during their occupation ( so 212-146 BC.) Did any Greek rulers recognize Rome as a serous threat? How Many Greeks regarded Rome as a potential allies? And what were Greek reactions to Romes rise and defeat of the all mighty Carthaginians? On a related note, How did Greeks justify their defeat? Did they blame themselves, the gods or other causes?
The Greeks viewed Rome as a new entrant in the Hellenistic state system. They were another major state like the Seleucid Empire or Egypt and thus they could be bartered with in the same way. The era was all about balance of power politics so we see shifting alliances fairly frequently.
Hellenistic states did not humbly submit to Rome. There were four Macedonian Wars, several wars with Mithridates, revolts all around Asia Minor and the Near East. In each of those wars and revolts you also see people welcoming Rome and allying with Rome to gain local advantages. Rome was far enough away to be a less demanding overlord than the other Hellenistic kingdoms or leagues.
As to the why, that is the very questions Polybius sought to answer in his history. Mostly he credits the Roman political system and their culture for creating a society that could withstand great loss and still strive for success.
If you want an exhaustive answer to this question you can read Erich Gruen's The Hellenistic World and the Coming of Rome. For a heavier focus on war you can read Arthur Eckstein's Mediterranean Anarchy. Both are weighty tomes but quite good for showing the social and cultural side of Rome's emergence in the Greek world (Gruen) and the international system which forced Rome to enter the East and allowed Rome's conquest (Eckstein).