Unfortunately I do not know enough about the original religions of Africa. In any case, the Christian (and any other) religion could be successful if its missionaries made it clear that the gods of the new religion were stronger and better than the divine forces that played a role in the indigenous peoples.
Seems to me that European and North American missionaries to Africa made a gross error in assuming that their role was to persuade people that their God was greater/better than the divine as experienced in African spaces. That's imperialism.
Rather, and some did this, their responsibility was to care for persons in the Name of the God they served and to share the Christian story as a way of understanding the meaning of life.
To put it another way, it seems to me that evangelism does not involve setting the God of Christian faith up as a competitor with other gods or divine beings. Rather, it is a matter of sharing our experience of who God is for us and who God might be for others.
1/ I think your reasoning is understandable and I personally can share it. The time of intense Christian Africa mission (of both great denominations) was the last decades of the 19th century. Spain, Portugal, the UK have historically been active missionaries worldwide since the discovery of India and the American continent, Germany only since 1884 (until the end of World War I). Since the victory of Islam in the Mediterranean region over the Christian Roman Empire, Islam played a considerable role in North, East and Central Africa (slavery was also known here long before the 17th century, although more with traders from Arabia/Asia than with Europe).
2/ Of course, sociologically and sociocritically, missionary work in the 19th century was part of imperialism. However, this did not exclude the possibility that missionaries, who were completely devoted to their work and also to the people in which they lived, would do exactly what you called humane reasoning.
3/ The Christian mission attracted above all the chiefs of the tribes with educational offers that belonged to careers in the modernized parts of Africa. They set up schools, introduced young people to craft trades, promoted modern farming methods, again supported by the white colonial administration, of course, but also had resistance when the white governor recruited the indigenous people into forced labor - as far as the available reports tell the truth.
The problem for the missionaries was that the villages they were missionizing had to be put in a position to live "Christianly" with better success - and independently as their own church without the whites - than was the case before. There was a big barrier for the chiefs: Islam allows several women if the man can feed them, Christianity demands monogamy. How is that supposed to work? The Christian gods - from the point of view of those affected - must be stronger if one submits to this. And I believe, but I have no proof, that the Christian mission here also worked with "carrot and stick", thus also threatened with hell and damnation, if the Christian converts do not fulfill God's commandments.
African religious space is dominated by foreign form of religious worship 'Christianity and Islam' these foreign religions were pioneered by the Arabs and the Europeans whose efforts were to supplant the African religion with theirs. they presented to the Africans more of their 'Arab and European culture' as is evident in the names, clothing style etc. the religious crisis in Africa is not unconnected to this fact.
Without having exact knowledge of the original forms of African religions your statement seems to me to point in the right direction. It could well be that in some parts of Africa today not only an increased turning to Islam is taking place at the expense of the earlier Christian mission work, but also efforts are present to bring the original religions back to light, at least as a task of religious studies and popular history. But nevertheless I know too little about it.
Christianity still maintain its ground, Islam feels threatened by the rapid growth of Christianity in West Africa. hence the Islamic onslaught on Christianity in West African. on the other hand African Traditional Religion has continued to play host to these two foreign religions that never reciprocated it gesture of love. interestingly both Christianity and Islam preach love but never loved each other.
Thanks for information. Yes religions which claim that they alone have truth don't love each other. But it would be interesting to get more information about religions of indigenious people in Africa. there were men and religions before the religions of Cnristian and Islamic faith existed.