Why did Kentucky fight on the side of the north?

[Minimalist]

Great point.

From what I understand, the North didn't give a crap about the black people. They just made the no slave rule so that the South would be dependent on them. I don't think any of the Union soldiers who went to war and gave their life for the cause cared one bit about black people. It was all about politics and power, not about slaves.

Yes, but oversimplified.

Had the north and south wanted to fight about slavery they could have done so anytime after the Missouri Compromise of 1820.  The fact that it took another 40 years says that there was something else going on.  There were a significant minority in the north known as abolitionists and a few in the south who did care, passionately.  They were largely kept out of power.  Yet, South Carolina seceded on 12-20-1860 and less than 4 months later Ft. Sumter was fired on.  So I tend to agree with your basic point that whites were willing to argue about slavery but that is a far cry from armies of 80,000 to 100,000 men shooting muskets and cannons at each other.  The trigger point for the war was rebellion, but there were significant other issues, not the least of which was the South's (correct) perception that the rapidly industrializing north was passing it by.

Again, a union recruiting poster from 1861.



and another,



I don't see a single word about "slavery" there.... nor do I hear anything about it in this song from Porter's Division, Army of the Potomac in 1861.





A southern tune....  they talk about their "rights" but note that those are unspecified.






The Bonnie Blue Flag was originally written in the winter of 1861 when the first 7 southern states seceded.  Later it was amended as succeeding states joined the confederacy.