Stating the cause of the Civil War was slavery is an oversimplification.
Stating the cause of the Civil War was not slavery is fallacious.
Well we know Abe wanted to ensconce slavery into the Constitution, if the South didn’t secede. We also know he intended to war on the South if they refused to abide by federal laws, like the recently passed Morrill Tariff that was passed without any southern votes. He made all this perfectly clear in his first inaugural speech.
He then set up events at Ft Sumter to invade the South. So, what can we conclude from this? There wouldn’t have been a war had Abe not invaded to impose the tariff. So from the aggressor’s point of view, the war wasn’t about slavery. It was about money.