There were many sectional differences in ideas, leadership, and future plans for the United States. Leaders from both sides had conflicting objectives and intentions.
Many issues were argued amidst the states and their leaders. Abraham Lincoln noticed the strong division growing between the northern and southern states and wanted to unit them. Lincoln wanted all states to be either slave or free just so long as they agreed. Confederate leaders however, did not want the uniting of states. They believed one government should not control all states; instead, they wanted individual states to be governed by themselves.
A main divergence was the topic of labor. More specifically, what was the better system of production? What was the most civilized way of working? Factory workers and slaves were the main source of labor. Northerners were disgusted with the South for owning slaves. They felt slavery was immoral and decadent. Southerners, however, deliberated that the North were hypocrites because of their poor working conditions.
The North relied on industries for income, and the South relied on cash crops. Mutually they believed their working arrangements were much better than that of the opposing side.
Industries provided mass production of widgets and various parts for assorted machinery. Unfortunately, the majority of employment used for industrial labor was provided through the services of extremely young children (sweat shops). Because of the extraneous activities, the life expectancy became shorter.
For the South, labor came from slaves. The slaves would mainly work on fields picking cotton, plowing and many other farming duties on plantations. Although living and working situations were at times considered better than those in the North, it wasn't justified. It was very difficult and demeaning. With the animosity growing, war was destined to occur.
One interpretation for the cause of the Civil War was that the North believed they were far more superior to the South. The North believed they had the moral high ground over the issue of slavery. Additional, they believed the South was erroneous for owning slaves and their actions were blasphemous and sinful. Because of that, the North believed they were a greater devout people.
Another interpreted cause was the argument over how states should be governed. The North, namely Abraham Lincoln, wanted one government to preside over the entire United States. He wanted for laws to be equal, either permitted or prohibited by all states similarly. The South wanted for individual states to possess individual rights.
My own hypothesis is that the striving for power and control erupted and caused the war. Both sides did not want to yield. Since they would not capitulate to the other, pride became a huge factor. This then turned into the motivation to prove which side was greater. Because of their sinful and selfish actions the bloodiest and most death-tolled war took place.