I’d say you should put more thought into this, particularly regarding your comment:
“I think we can agree that it had nothing to do with caring about the slaves.”
Sounds like you’ve been brainwashed into oblivion by Howard Zinn.
I should have clarified it. For the easily manipulatable, it would have been about slavery. But for those at the top, it would have been about keeping wages as low as possible for as long as possible, so they can buy up southern assets for a song.
I see a lot of the same movements in this as I do with globalism, where those advocating open borders to keep wage earners earning as little as possible for as long as possible.
The average union soldier was NOT fighting to free slaves.