No, no, Zinc man, he's brass, not bronze.
It was about slavery, but also state's rights. The Tariff of Abominations nearly provoked the Civil War 30 years earlier, and that said nothing about slavery. There was legitimately a strong disagreement about the proper extent of federal power, dating back to the Constitutional Convention; slavery was the primary flashpoint where the southern states disagreed with the Feds's majority, but not the only one.
It came down to economics, but that's hardly notable; war almost always does. War is expensive and destructive and so it generally only happens when there is a whole lot of wealth to be won and lost.
Certainly it was about multiple issues. But I will note you didn't actually address the bulk of what I said. Which was evidence in the confederate constitution that when slavery and states' rights came into conflict, they prioritized slavery. I can say I value honesty and I value my family. But when they come into conflict the one I choose shows where my priorities are. The confederate constitution, through the use of multiple different clauses working in concert, specifically limits the ability of confederate states to outlaw slavery, even if the state decided to. So slavery was more important than states rights. Just like if I chose family over honesty in my other example. That is flat out proof that slavery was more important than states rights. Because in their own laws they prioritized slavery over the rights of the confederate states. People can say what they want, but the evidence of what they actually made law is right there to see.
So while, yes, the American Civil War had a whole bunch of complicated issues, it is still clearly shown by the Confederacy's own laws that slavery mattered more to them than states' rights. These aren't mutually exclusive. A situation can be complex, and still have evidence that one part is being treated as a higher priority than the others. Which the Confederacy did, by making laws that limited states rights when it came to slavery where the two were in conflict.