The fact that some Americans supported slavery in the eighteenth century is not at all remarkable. Most of the world agreed with them. What is remarkable is that many of them sought to abolish slavery in the new republic.
Historically, Europeans had few qualms about conquering and enslaving other Europeans. This presents some problems for the narrative claiming that injustices committed by Europeans are motivated primarily by racism.
In a slave economy, slave owners seek technological innovations that make slave labor more productive. But they also place inefficient and artificial limits on innovations that might change the established social order.