You're being too reductive. There is no simple one sentence answer and the path to modern western liberal values spans 400-ish years.

It wasn't really that long ago that all/most societies believed that slavery was normal.

Just the IDEA that "all men are created equal" is intensely liberal. And that it was put into a document without qualifiers is miraculous. We can't judge the past only from a modern lens. YOU didn't do anything to help the world move towards liberal values. YOU are just the benefactor of thousands of years of conflict/learning/etc.