It took a long time for you to form YOUR OPINION.
Sorry, it is not my opinion that all 7 of the Lincoln-Douglas debates heavily featured the topic of slavery.
It is not my opinion that “Uncle Tom’s Cabin” was the 1st book in United States history to sell 1.5 million copies, at a time when books were still scarce in general possession. Only the Bible sold more volumes than Uncle Tom’s up to that date. That is NOT opinion.
It is not my opinion that the Vice President of the Confederacy declared that slavery was the reason for secession.
So you can pretend that it is only my opinion that slavery was the foremost cause of Southern state cessation that caused the Civll War, but it is a fact, even as the issue of State sovereignty followed closely.