Business
The same capitalists who promoted slavery later helped end it. While their wealth depended on the slave colonies they ignored or defended slavery, and once that protected colonial trade became a nuisance to a maturing industrial economy, they turned against it.
Slavery was not born of racism; racism was the consequence of slavery. Planters first worked unfree laborers of every color and creed, and only later built ideas of racial inferiority to justify the labor system they had settled on.
Employers picked enslaved Africans over white servants for practical reasons: they were cheaper, and their visible difference made escape harder. A runaway servant could blend in, while an enslaved African was conspicuous by color and features, so the system chose the workforce it could hold most cheaply.
Fortunes made by plantation owners, shipbuilders and merchants in the slave trade flowed into banks and heavy industry. That accumulated money helped finance the Industrial Revolution, so modern capitalism was built partly on slavery rather than beside it.
Ending the slave trade and then slavery was driven more by economic self-interest than by humanitarian feeling. Reforms tend to win when they stop costing the powerful money, and the moral story told afterward hides that shift in interests.
Explaining abolition as the triumph of kind-hearted reformers keeps the powerful at the center of the story. Crediting their conscience pushes aside both the economic motives and the people who actually fought their way out of bondage.
The enslaved were central to breaking their own chains. Their resistance raised the cost and risk of keeping the system going, and those rising costs fed directly into the financial calculations of the people who ran it.
Ending the slave trade first reduced the number of enslaved people in the empire, which made ending slavery itself easier later. Cutting off a system's supply weakens it, so the final ban meets less resistance.
Readers of African descent uniformly praised the argument, while those of European heritage were cooler and divided. An account that removes a group's flattering role in history tends to be resisted most by that group.