Here you make my point for me that I was trying to make to SoCal Pubbie in previous exchanges. They were telling the various audiences what they thought those audiences wanted to hear. For Southern voters, they were claiming it was because the North was threatening slavery. (it wasn't and couldn't.) To Europeans, it was because the North was preventing free trade.
The truth is they realized not only would they make more profits from direct trade with Europe, they also wouldn't be constantly outvoted in congress over every question concerning their interests. They would go from little fish in a big pond, to big fish in a smaller pond, as well as getting richer into the bargain.
Also they were probably tired of hearing moral lectures and condemnation from representatives of the Northern liberals. It was likely the same as those lectures we hear from modern liberals about the immorality of using fossil fuels. (which is our modern economic engine.)
I don't necessarily disagree, but you're telling me that like any good Democrats they didn't really believe their own propaganda, it was all for show.
Your problem is that many -- indeed the vast majority -- did believe their own propaganda because, to them, it was true: "Ape" Lincoln and his "Black Republicans" threatened slavery enough to make secession "necessary".
The fact that Lincoln did not really threaten slavery makes secessionist propaganda a Big Lie which converts the "necessity" into pure, unadulterated at pleasure secession.
It's an important point in making the Confederacy illegitimate from Day One.