Pls expound on both bolded sir.
Regional pantheons associated with different peoples were the major "religion" among Africans. Remember, the actual triangle trade went on for about 300 years.. Certain regions became hotbeds for slave acquisition , this would lead to a rise in the prominence of that religion among the slaves and that would rise and fall. So, the Yoruba religion, which has a bunch of different 'gods' (They would call them Orishas) is probably the most influential of our original religions. That would be an example of a regional pantheon practiced by our people prior to slavery. You can still see it all over the diaspora like
Brasil
Cuba
Trinidad
21 Savage practices Yoruba religion and it's quite big in Atlanta (inb4 'i aint from africa im from crenshaw mafia' nikkas get mad)
To answer your question.. We did not have one precise religion, but a multitude of regional ones that weren't nearly as "religion" ish with books and dietary laws and allat we would associate with Abraham religions.
Your second question speaks to a really broad historical issue with a bunch of different answers (Our people interacted with Islam in different ways in different places.) However, the plurality of Islamic adherents in Africa at the time of the slave trade became Muslim under repressive Arabized regimes that did not like Black people.
13 Shocking Insights Into Islam and the African Continent
Short read on it.
In sub-Saharan Africa, people often converted to Islam to keep trade open and to avoid being sold into slavery. Africans believed Islamic conversion would create mutual respect but since slavery is justified in the Quran, there was no guarantee of avoiding bondage.