Or maybe Anderson and the unionists were prescient about the the south’s inability to hold on to it. ;-)
The South held Fort Sumter for almost 4 years holding off amphibious assaults by troops, ironclad attacks, large bombardments from shore batteries, and a threat to bombard Charleston civilians unless the Confederates give up their forts. That noble bombardment of civilians by the Union went on for 18 months, but the Confederate still held Sumter. The Confederates left the fort in February (I think it was February) 1865 when Confederate forces were ordered to North Carolina to help fight Sherman.
Um, how long did Anderson hold out after he came under fire?