It doesn't. It requires nuance and a whole lot of historical context. Slavery was certainly a factor, but it was one of many.
Two small points to get you started.
1. The causes of secession and the cause of the war were not the same thing. The former had many, the latter was entirely economic.
2. Only 4 states even issued declarations. 3 of them were heavily about slavery. The rest require historical context to understand. Slavery wasn't even under threat if states had just hung around. You need look no further than Lincolns inaugural speech to verify that.
If slavery was one of many factors for secession, why weren't any of those other factors mentioned in the ordinances of secession? Why were all of the seceding states slave states? Of the states who didn't mention a reason for secession in their ordinances of secession, all their governors made statements explicitly naming slavery as the reason (see previous link).
> Slavery wasn't even under threat if states had just hung around.
The Kansas-Nebraska Act threatened to tip the balance of slave states vs. free states, and Lincoln's and the Republican Party's platform of not allowing the creation of any new slave states effectively put an expiration date on slavery in the US. That is why the ordinances of secession mentioned the threat against slavery. Lincoln only stated that he wouldn't directly abolish slavery because the slave states had already threatened to secede if he were elected, citing the belief that he would.
You keep harping on the cause of secession, not war. Again, there were different causes for each state.
I've been down this discussion road many time before and it goes on for a while with a lot of back and forth. The simplest thing for you to do is to go and grab a couple of books on the civil war, read them and when you get to something that seems impossible based on what you currently know go and look up the citations. The digitized Library of Congress and Google's efforts to scan historical documents make it really easy to read while verifying.
Since you're harping on the causes for secession, I'm going to go ahead and provide you a couple of quick links to refute your stance to get you started though:
This includes the declarations of Georgia, Texas, South Carolina and Mississippi. Georgia, Texas and Mississippi were almost entirely about slavery. South Carolina's was partially about slavery. You can see a graph here with a breakdown of each document (http://www.civilwar.org/education/history/secession/).
That first link also includes Virginia's secession ordinance at the bottom, which isn't a declaration of causes but merely the bill passed to secede. You'll notice no mention of slavery, but instead the perversion of federal power. The only mention of the word slave is the oppression of not only Virginia "but the southern slave holding states".
Now, hop on over to timeline of events on Wikipedia:
Jump down to 1861, then look at Feb 4, April 4, April 15 and then April 15-16, April 17-19 (really most of the "Aftermath 1861" section).
To summarize, you'll see Virginia unwilling to secede (... only 32 of 152 are immediate secessionists...), Virginia again reject secession, Lincoln bypass congress to request troops from each state. Following this request for troops is when the remaining states secede (Virginia, North Carolina, Tennessee).
For these states, they were not seceding "because slavery" they were seceding because the Federal government was bypassing Congress to start a war and had no intention of taking up arms against the south. The way in which the war was fought did not help the case.
Now, that should put most of the idea of a single cause of secession to rest. What I would suggest next is for you to grab a book on the economics of the civil war (because there are many).
Just to give you a hint of exactly how big of an issue this was...
March 18, 1861 the Philadelphia Press wrote: "Blockade Southern Ports. If not a series of customs houses will be required on the vast inland border from the Atlantic to West Texas. Worse still, with no protective tariff, European goods will under-price Northern goods in Southern markets. Cotton for Northern mills will be charged an export tax. This will cripple the clothing industries and make British mills prosper. Finally, the great inland waterways, the Mississippi, the Missouri and the Ohio Rivers, will be subject to Southern tolls."
March 22, 1861 the economic editor of the New York Times wrote, "At once shut down every Southern port, destroy its commerce and bring utter ruin on the Confederate states."
That's before we even get into why John Brown is famous, because he never actually accomplished anything. The only reason we know his name is that he lit a match on a lot of southern fears and northern sentiments. You can even see this played out in the Emancipation Proclamation because it was issued twice - the first time as a warning.
I'm not even pretending that slavery wasn't a major factor, just refuting the idea that it was the only factor. The war was about money and fear, from both sides for different reasons.
Again, there is no debate among historians about why the states seceded. See the final link in my previous post.
> You'll notice no mention of slavery, but instead the perversion of federal power. The only mention of the word slave is the oppression of not only Virginia "but the southern slave holding states".
The perversion of federal power mentioned is the new government's coming actions to eventually kill slavery. Again, the governor of Virginia said as much (“The Northern States must strike from their statute books their personal liberty bills, and fulfill their consitutional obligations in regard to fugitive slaves and fugitives from justice. If our slaves escape into non-slaveholding states, they must be delivered up.”) Again, no other cause is mentioned by any of the states.
> For these states, they were not seceding "because slavery" they were seceding because the Federal government was bypassing Congress to start a war and had no intention of taking up arms against the south.
They didn't like Lincoln's call for volunteers to bring the seceding states in line, yet they had no qualms about immediately raising troops via draft (via the first conscription law in the United States) to fight against the Union. Why is that? You noticed that your Wikipedia link about the timeline of events leading to secession is all about the history of slavery regulation in the United States, right?
Your quotes are proposals of what to do with Southern states that seceded, not the cause of secession.
You're going into mental contortions to disagree with historians. Why?
I'm not going to overinvest my time here because this is a long road. All my above points stand, but you need to reread them.
The quotes were to provide you with context on the economic impact secession was going to have on the northern economy (which would have been devastating). I'm well aware of everything left out of the Wikipedia timeline, but it's a locked topic with 15,000 plus edits.
If you want a better understanding of the subject, there are a lot of books to satisfy your curiousity.
Two small points to get you started.
1. The causes of secession and the cause of the war were not the same thing. The former had many, the latter was entirely economic.
2. Only 4 states even issued declarations. 3 of them were heavily about slavery. The rest require historical context to understand. Slavery wasn't even under threat if states had just hung around. You need look no further than Lincolns inaugural speech to verify that.