"Wait, why is Christianity getting the credit again?"

Let's see:

The classical world had no real moral system except might makes right. This was true of the Greeks, the Roman, the Germanic tribes, the Babylonian, The Persian, Etc.

Judaism came up with this revolutionary idea that other people should be given moral consideration, even the poor, even the reviled, even one's enemies.

Along comes Christianity and makes that into a universal moral imperative, one that ultimately informed our worldview today. Indeed, we can trace that imperative to various particular Christian texts, such as the gospel, Paul's epistles, the writings of Augustine.

Which is why we ask if some action is right or wrong -- that wasn't really an issue in the classical world.

Does that help?