Mine is more of an opinion, but all the forts located in Texas and interior States where there was no water, the fort was abandoned as it was that particular States property the fort stood on. The island where Ft Sumpter stood, was considered South Carolina property and thus should have been vacated as the interior forts. Just because the Federal Government built the fort, at that time in history, the land was the property was State.

Today we have US military installations which is Federal property. Back then the States guarded their property from Federal encroachment.