If you are a slave, living in a country where slavery is still being practiced, then you have two options.
#1. Migrate / run-away to another country and live a happy life there
#2. Organize all the slaves and try to seize power.
#2 is only viable if the slaves are in a majority.
BTW.... it seems that you would like to assume that only blacks were taken as slaves. In the recorded history, blacks consisted only of a minority of all people who were taken as slaves. The Atlantic Slave Trade enslaved some 12 million people, while the Arab slave trade enslaved another 18 million.
On the other hand, just the Crimean-Nogai raids into East Slavic lands alone enslaved some 3 million Slavs. And the Spanish conquistadors enslaved tens of millions of native Americans in the Latin America.
You cannot deny that we had the most gruesome history of slavery. America is the only nation that fought a Civil War based on slavery.