While the Enlightenment may not have directly led to the abolishment of slavery, it certainly started to change the minds of those in a position to oppose it.
While on the face of it, the Union fought for the abolishment of slavery, the main reason that Lincoln took the country to war was the preservation of the Union.
The new document was a novel and unprecedented concept that would have undermined the monarchy and the status quo, and the abolishment of the feudal system would further disrupt the system.