It is not what the Confederate Constitution said about slavery that caused the Union to invade it. It was what it said about being independent of the Union's financial controls that convinced the Union that it had to be invaded.
The South's reasons for leaving don't matter. Presumably if they left because they didn't like Northern grown apples, the Union would still have invaded. It is the North's reasons for sending men to die to stop Independence that matter.
Those reasons boil down to money. Who would lose it, and who would gain it.
The North invaded the South? Jeez, I like how you left out that little dust up at Ft. Sumter. Why don’t you put out your f**king lamp and go to sleep. It’s past your bed time.