Why did Kentucky fight on the side of the north?

[Aroura]

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.

While it is true to say that Lincoln was more concerned with holding that nation together than slavery, or that the north's response was not only about slavery, the north did not come up with the no slave rule so the south would be dependent, nor is it true to say, as a blanket statement "the North" didn't give a crap about black people.  Both of these statements are patently false.

The irony is that we think the South went to war over states rights, but that is bull.  It succeeded in order to protect slavery.  

So what you have is some states outlawing slavery, the abolitionist movement.  This happened before the succession, and was indeed begun by people arguing that owning other people was wrong.  It spread. The fear that abolition would become a national position caused the southern states to succeed.  Now, did the north say no to the succession only because of slavery?  No.  They said no to hold the union together.  But the war absolutely was about slavery.  The states who succeeded desired to protect the institution of slavery. 

The cause of the war:  The south wanted to protect the institution of slavery, which was falling out of popularity, and the north fought to keep the south as part of the union.  

---

If the civil war was all about slavery, or slavery was the primary issue, why did Kentucky (a slave state) fight on the side of the north? Why did they in general, even regardless of that issue?

If you are going to present and argument, at least make it accurate.

Kentucky sent 35k troops to the confederacy

Yes, it also sent troops north, but Kentucky was clearly a split state.  To say the "fought on the side of the north" entirely misses that they also fought on the side of the south.