I don't think it was all that complex when you visualize it properly.
Most of that money belonged to the South. The North wanted to keep it.
You are both partially right. The war was about slavery in large part; but it was not solely about slavery; it was also largely about economics and politics. It’s fair to say that the war was about both the ethics and the practicality of slavery, and whether it would sustain or undermine our Constitutional republic. Less than a century after our unprecedented Revolution, the developing American experiment was fragile.
There are parallels to today’s exploitation of illegal immigration and foreign proxy wars enabled by the corrupted government and the taxes extracted from all of us. Whether individual citizens agree with these conditions or not, we are coerced to support them economically. Our consciences are insultated because for the time being, our nation is wealthier, so that we don’t regard our double standards quite as guiltfully as we regard 19th century American chattel slavery—but future generations may not agree.
However, as regards the CW—no one reason, but rather a complex stew of human impulses from best to worst drove both the North and the South into war.
Once it broke out, decent people in both regions were forced to take sides with the “least worse” side, according to their situation (like our presidential elections today). The poor, as always, have the narrowest range of choices. Many ended up cannon fodder, or widows and orphans.
Bellicose opponents always try to paint the other side with the worst accusations, but the side that “won” the war gets to write the history books, and have their narratives regarded as more true. Eventually, cooler heads evaluate a wider range of factors.
But not always.
I don't think it was all that complex when you visualize it properly.
Most of that money belonged to the South. The North wanted to keep it.