West Africans were not practicing Christianity BEFORE or colonialism or slavery.
You think they picked up a free copy of the bible on board one of the Slave Ships on the way to the west?
Yh it's nice you can pick and choose whatever region you want to practice but MOST people are born into the faith they are currently in.
Like what is so hard to understand about that? I'm not typing English?
Look at the biggest black diasporas in the world, Brazil and The Caribbean, their ancestors were slaves brought over from West Africa, what is their main religion? Christianity.