There is no doubt that the South fought the War to preserve slavery. You get into the realm of quacks and fanatics to believe any other reason was significant.
It’s fear of the North’s growing power led to the conclusion that already a minority it would become even more so and decided to fight.
George Washington’s Farewell Address warned of the designing men who would urge secession. That was the main point of the address.
How was slavery endangered by remaining in the Union? If you are going to make such a claim, I expect you to support it.
I've seen this claim numerous times, but when people are asked to point out how slavery was going to be in danger, they say, "Uh, if it didn't expand it would cease to exist!" as if this claim were some how self evidently true, which it isn't.
I've shown up thread that expanding it was impossible, even if everyone agreed to it. The land into which it would have to expand, wouldn't support it.
So how was the South fighting a war to preserve something that wasn't really in any danger? Riddle me that.