Irrelevant. Focusing on their alleged reasons for wanting to leave is dismissing their right to leave. Their reasons for leaving may have been morally wrong or even stupid, but you cannot gainsay someone's right to do something because you don't like why they want to do it.
And that being said, Paul Craig Roberts argues their claims of wanting to leave over slavery were simply intended to be a clever legal strategy for getting out of the contract that was the US Constitution. By arguing that the Northern states had breached the contract first, it gives them the legal right to revoke the contract. In other words, all the statements claiming this was the reason were just a ploy.
https://www.paulcraigroberts.org/2018/11/13/a-civil-war-lesson-for-the-uneducated/
With the US Congress and the Northern states willing to vote to pass a slavery forever amendment, the fact that the Southern states didn't accept this deal implies that Paul Craig Roberts is correct. They weren't after protection for slavery, they were after the money and used "slavery" as an excuse to get out of the contract.
As for the claimed "right" to secede, it fails basic law and logic in that it supposed the Constitution was a contract subject to an unwritten right to secede based on the election of Lincoln because he was against slavery. Yet the contract analogy fails because Lincoln had not acted against slavery, so there was no breach of contract that justified secession as a remedy. Of course, to the degree that the Constitution was a contract, entry into it was a one time thing, not a gate that could be opened or closed as circumstances dictated.
No serious historian buys into the Lost Cause myth that secession was prompted by tariffs and other economic issues. The historical record is plainly to the contrary, with Confederate secession based on the determination of the South's slave owning elite to maintain slavery.
By the way, Paul Craig Roberts is an economist, not a historian. Accepting his opinion on the subject of slavery and secession is like relying on an airplane mechanic for guidance on cancer diagnosis and treatment.
Regardless of what DiogenesLamp claims, no Founder believed in an unlimited "right of secession" at pleasure.
Instead, they believed in and practiced "secession" or dis-union under only two very limited circumstances:
We should acknowledge that DiognesLamp hates that, more than Indian Jones hates snakes -- DiogenesLamp wants anyone to be allowed to secede at any time, for any reason, or for no reason, it doesn't matter because secession is a "natural right" in DiogenesLamp's mind.
But that was not the belief of our Founders, and it is their Constitution that conservatives are committed to protect, preserve and defend, so help us God.