I think your timing is off.
My recollection is that the abolitionist movement became a major force long after the trans atlantic slave trade became illegal.
It may be that the sons and grandsons of the shippers, bankers, and traders became abolitionists. In that sense, it was probably a mark of sincerity that they spend the money gained though the slave trade on the abolition of slavery.
N
in LATE 1864, several of "the leading abolitionists" had stock in companies, which were still in the "flesh trade". they had MOSTLY moved their marketplace to BRAZIL.
same people, same companies, same FILTHY slave trade, SAME HYPOCRYTES too. (new englanders have ALWAYS been INTOLERENT & HYPOCRYTES! they still are, with their mostly LILLY-WHITE SCHOOLS, LOUD-mouthed arrogance & condescension!)
free dixie,sw