I'm not arguing that Christianity and Paul were irrelevant. I'm arguing that you're putting too much weight on them. We know opposition to slavery is ancient; Aristotle supported slavery, but he acknowledged that others didn't: “For some thinkers hold the function of the master to be a definite science, and moreover think that household management, mastership, statesmanship and monarchy are the same thing, as we said at the beginning of the treatise; others however maintain that for one man to be another man’s master is contrary to nature, because it is only convention that makes the one a slave and the other a freeman and there is no difference between them by nature, and that therefore it is unjust, for it is based on force.”

What's most significant about the Bible and abolitionism is it wasn't used in a major way to oppose slavery until 18th century, so clearly, Paul was not all that effective.

And since the early abolitionists included Deists like Franklin and atheists like Paine, it's hard to give the credit to Paul.

Mind you, I agree Christianity is incompatible with slavery, just as it's incompatible with capitalism. But Christians find amazing ways to rationalize greed and exploitation.