Missionaries came to East Africa for various reasons. These were economic, social, humanitarian and economic in nature as explained below;
The missionaries had the ambition to spread Christianity to the people of East Africa. This would be through preaching and teaching the holy gospel so that many would get converted to Christianity.
They wanted to fight against slave trade in East Africa. Earlier travelers like John Speke and James Grant, H.M. Stanley, Dr. David Livingstone and others had reported about the evils of slave trade in East Africa. Christian missionaries therefore came with an intention to stop it and introduce legitimate trade.
Missionaries wanted settle the freed slaves in East Africa by setting up resettlement centers both in the interior and at the coast for example at Bagamoyo and Frere town near Mombasa.
They wanted to check on the spread of Islam in East Africa from the coast with intentions of converting many to Christianity.
Some missionaries came because they had been invited by certain African chiefs, For example, Muteesa I of Buganda wrote a letter through H.M Stanley inviting missionaries to Buganda.
They came to establish legitimate trade in East Africa. They, for instance wanted to trade in items like glass, cloths, etc. as Dr. Livingstone told Cambridge University students, “I go back to Africa to make an open pass for commerce and Christianity…..” Similarly, his speech in 1857 emphasized the unity between Christianity and Commerce.
The missionaries also loved to adventure and explore the interior of East Africa. For example Dr. John Ludwig Kraft of CMS is said to have been the first European to see Mt. Kenya while Johann Redman was the first to see Mt. Kilimanjaro.
They had a mission to clear the way for the colonization of East Africa. The missionaries were tasked by their home governments to preach ideas of love, respect, brotherhood, forgiveness, tolerance and non violence so that when the colonialists come, they would meet less resistance from the East Africans.
It’s also argued that missionaries wanted to “civilize” East Africans. They argued that they came to stop some of the barbaric acts and customs e.g. Female Genital Mutilation among the Kikuyu in Kenya, human sacrifices and the practice of killing twins.
They had interest of reducing tribal conflicts in East Africa. E.g. conflicts between Buganda and Banyoro would be resolved with the coming of the Missionaries.
Early contacts by travelers like Stanley, Speke and Grant, among others encouraged missionaries to come. The information they gave about important places like the source of the Nile, fertile soils, river falls and the climate all attracted the missionaries into East Africa.
The expulsion of some of the missionaries from other parts of Africa led them into East Africa. For example Johann Ludwig Kraft and Johann Redman are said to have been expelled from Ethiopia around 1842 before they chose to relocate to East Africa.