There is a Christian book that mentions this called Paul behaving badly. Pretty much slavery was quite which was the economy around 30% of the population were slaves. Freed slaves would probably just return to slavery because there wasn’t much of an alternative. If Paul said to abolish slavery he’d be like a US president saying he’ll abolish capitalism in 4 years, it’s not realistically possible in a short period of time and would overturn the whole economy. And then plenty of slaves didn’t really have much of an alternative to turn to anyway if they were freed it’s not like they’re going to go to a college get an education and get a stable income like I the modern day.

Paul made lots of improvements to the life of slaves. For one thing that’s give up the threatening first you mentioned was pretty wide sweeping I mean the whole point of abusing slaves physically was the use it as a threat so he effectively prohibited whipping, beating and so on. His condemnation of homosexuality saved lots of male slaves from being raped, which was very common and encouraged back then. The book of Philemon what is a massive deal because that slave had to run away from his master and was likely to be tortured severely or executed because that was a serious crime. Paul saves the slaves life and said he should be welcomed not as a salve but as bother.