It is more important to look at what motivated the abolitionists though, not the slaveholders.
The single most important event in the process towards ending of slavery was the British ban on the slave trade, and this was the result of what was very much a religious movement. It wasn't simple 'people who happened to be Christian', but people specifically motivated by religious fervour: Quakers and Evangelical Anglicans.
Anthony Benezet’s propaganda campaign had its most pronounced impact in Great Britain. Nowhere else among the major slave-trading powers did a popular, public campaign against the traders emerge. That this campaign crystallized in Britain at the close of the eighteenth century might seem odd at first glance. In the second half of the eighteenth century, British merchants were the leading slave traders in the Atlantic world. There were good commercial and political reasons to favour a continuation of the trade.
Antislavery sentiments, moreover, did not always lead to antislavery commitments. That seems to be one lesson that arises from the history of antislavery thought in France, where there was a critique of the trade’s inhumanity but only the most minimal attempt to address it (Seeber, 1937; Miller, 2008).
It would be a mistake also to attribute the new antislavery campaigns to the cultural consequences of merchant capitalism, as the historian Thomas Haskell once proposed, given the complete absence of abolitionist organizing in the Netherlands, where merchant capitalism was strong (Bender, 1992).
A number of historians have detailed how the first British abolition campaign came to fruition in the 1780s – the Quaker petition to the House of Commons calling for abolition, the alliance between Quakers and Evangelicals that culminated in the formation of the London Committee for Effecting the Abolition of the Slave Trade in 1787, and the series of investigations and debates in parliament that raised and then thwarted hopes before the somewhat sudden achievement of abolition in 1807 (Anstey, 1975; Oldfield, 1995; Jennings, 1997).
Only recently, however, has the prior transition from antislavery thought to antislavery action received close scrutiny. The formation of antislavery commitments in the British Isles during the 1780s depended in part upon the changing politics of empire that attended the expansion of British dominions after the Seven Years’ War and the loss of 13 North American colonies in the American Revolution.
A new concern developed in this period that imperial practices needed to be assessed against the standards of virtue and liberty. Among Quakers in England, and among aspiring young reformers within the Church of England, Thomas Clarkson and William Wilberforce most notably, turning the nation against the Atlantic slave trade looked to be one way to improve the moral character of overseas enterprise and to foster a greater commitment to religion at home (Brown, 2006: pt III, IV).”
Heuman, G, Burnard, T. - The Routledge History of Slavery
The
Clapham Sect or
Clapham Saints were a group of
Church of England social reformers based in
Clapham, London, at the beginning of the 19th century (active 1780s–1840s).
The members of the Clapham group were chiefly prominent and wealthy
evangelical Anglicans who shared common political and social views concerning the
liberation of slaves,
[1] the abolition of the
slave trade and the
reform of the penal system, amongst other issues, and who worked laboriously towards these ends over many years, motivated by their
Christian faith and concern for
social justice and fairness for all.
Clapham Sect - Wikipedia