I don't know where you are getting your ideas from. The printing press was invented in Europe in 1453 (15th century) and last vestiges of slavery were abolished in Europe and the US in the latter half of the 19th century, more than 400 years later.
In addition to that, there was no need to wait the printing press: there were tens of thousands of hand-made copies of the Bible available (the so-called 'majority text').
And even after they were printed en masse, most of the people were illiterate and couldn't read them, let alone afford them!
People first must free themselves from the tyranny of warlords before they can free anyone else.
Also....I suggest that you do a Google search in the words: “Gutenberg, Literacy, and rise”. You will see that literacy spread rapidly throughout Europe after the invention of the printing press in the mid-1450s.
The big breakthrough was Luther's and Tyndall translations of the bible in the early 1500s. There is a reason the English warlord, King Henry VIII, burned William Tyndall at the stake. The bible is a genuine threat to any tyrant's power. Imagine that! We are equal in the sight of God!
The warlords of Europe were tamed because the common people understood that if we are equal in the sight of God, then we must also be equal when standing before earthly law. The common people demanded it and got it.
Once free they could turn their attention to others. It was Christians, especially, and their tireless preaching and work that finally abolished slavery throughout the world. Please do a Google on William Wiberforce and his tireless work.
But...I suppose you would prefer to hold to your anti-Christian prejudices. Where did you learn this? A government K-12 school? A university?
The rule of law, peace, freedom from slavery, and prosperity that you and I enjoy to today is built entirely upon the philosophy of Christianity. We no longer need to be tribal with allegiance only to our clan. We can trust our neighbor and others beyond our tiny village. Trade is possible because we have honest courts to enforce contracts.
Destroy Christianity and we will soon be living under warlords like the barbarians in Somalia.
Surely, I hope you do not stand with those bigots who hate Christianity.