Those Africans who voluntarily converted to Christianity before the colonial conquest such as Affonso I of the BaKongo in the 15th century probably did not discern the purpose of the brand of Christianity that was supplied to them. Which was probably why they fell easy prey to the missionaries and the white traders and pirates who followed them.
But their Japanese counterparts probably did discern the game, even without access to some version of Leopold’s letter. But even if the Japanese Shoguns did not intuit what Leopold makes explicit, they clearly realized the danger of Japanese converts to Christianity forming a fifth column within Japanese society and state, a fifth column loyal to their co-religionists in Europe.
To rid Japan of that danger, in the late 16th century, the Shoguns began their expulsion of Portuguese and Spanish missionaries on the grounds that they were forcing Japanese to become Christian, teaching their disciples to wreck temples, taking and trading slaves, etc.
Then, in 1596, it became clear to the Japanese authorities that Christianization had been a prelude to Spanish conquest of other lands; and it quickly dawned on them that a fifth column loyal to Rome and controlled by the priests of a foreign religion was a clear and present danger to the sovereignty of a newly unified Japan.
Soon after, the persecution and suppression of Japanese Christians began. Early in the 17th century, sensing the danger from a creed that taught obedience to foreign priests rather than the Japanese authorities, all missionaries were ordered to leave and all Japanese were ordered to register at the Buddhist temples. When Japanese Christians took part in a rebellion, foreign priests were executed, the Spanish were expelled and Japanese Christians were forbidden to travel abroad.
After another rebellion, largely by Christians, was put down, the Japanese Christians were suppressed and their descendants were put under close state surveillance for centuries thereafter. In the 1640s all Japanese suspected of being Christians were ruthlessly exterminated. Thus did Japan, by 1650, save itself from the first European attempt to mentally subvert, conquer and colonize it.
The African captives who were taken abroad and enslaved, and the Africans at home after the European conquest, having already been forcibly deprived of their autonomy, were in no political position to resist Christianization. Thus the Christianity still practised in all of the African American diaspora, just as that in the African homeland since the start of the 20th century, continues to carry out the Leopoldian mandate.
Hence, for example, whereas the White Born-Agains of the USA, when in the US Navy ships in WWII, sang:
“Praise the Lord,
And pass the ammunition,” the attitude of African Born-Again converts today is best summed up as :
“Praise the Lord,
And lie down for the manna.”
Thanks to a century or more of this Leopold-mandated missionary mind control, African Christians are not an activist, self-helping, economically engaged, politically resolute, let alone militant bunch. Hence their putting up with all manner of mistreatment and exploitation by their misrulers, white and black. The most they are disposed to do to their misrulers is to admonish them to “Fear God!”