The southern strategy was screwup after mis~step after tragedy. If the southern states had seceded and then simply stood back and built their industrial defense base while initiating no military force they probably would have won.
If you read the correspondence of Secessionist Leaders, at the time of the firing on Fort Sumter, they were afraid that if there wasn’t a war, no further states would secede (the Virginia Convention had already voted to remain in the Union unless war came). Davis thought that without a War of Independence, the states which had seceded would drift back into the Union by shear inertia, since there was a lot of pro-Union sentiment even in the Deep South.