What you have written here is misleading.
Natural Law grew out of the Hellenistic schools of Philosophy in ancient Greece. Sure they were Pagan, as was Aristotle, who also embraced the concept, but that doesn’t alter the cogency of the Theory of Natural Law. Anyone with a degree of rationality will always come back to the question of a First Mover, as did the Stoics and Aristotle. The ancient Roman’s also embraced Natural Law and Cicero is is bect known champion. The ‘Catholicness’ of Natural Law is usually sheeted home to Aquinas, however it was embraced by the Byzantines and codified into Law by the Emperor Justinian, himself, of course, a devout Catholic. From the time of the Roman Emperor Constantine, Catholicism was “the” religion of Europe and Natural Law ethical theory underpinned its development. Obviously, before the advent of Jesus Christ, there were no Christians, yet the obviousness of the cogency and coherency of Natural Law was there for the thinkers of what you call the ‘pagan societies’. So, has it cogency and coherence been obvious to some of the world’s most famous thinkers since then.
By the way, Judaism and Islam are also Natural Law religions, so one needen’t be Catholic, or even Christian, to recognise its existence and value.