If there's anything the 21st century has shown us, it's that most people are not intellectually ready for cynicism.
The vast bulk of political actors (whether soldiers, leaders, or bureaucrats) in history were ideologically motivated. People like to believe in things.
Calliope
Nearly 180,000 Black men served in the Union Army. Another 19,000 in the Navy. Black soldiers accounted for roughly 10% of Union military deaths. A large portion of each were formerly enslaved.
I imagine they gave a damn about slavery.