In fairness, the Confederates gave the Union the excuse they needed to beat them into submission by firing on federal troops at fort Sumter. If they hadn’t have done that, the Feds would probably have just had to let them go.
It’s true Davis made a huge mistake.
But fighting would soon have broken out over something else.
There was an immense number of potential conflicts, ranging from borders to who got the territories, etc.
The period between the first round of secession and Sumter was an extended chess game for advantage in the remaining unseceded slave states.
Had they all gone with the Union, the War would have been over in less than a year, and slavery would have continued roughly as before in the reunited Union.
Had all the slave states gone with the CSA, the War would also have been short, and the CSA’s independence would have been permanently established, though followup wars would have been almost certain.
What actually happened was the the unseced slave states split almost exactly down the middle, resulting in a long, bloody war ending only when the CSA was pounded into reluctant submission.