It was more defensible than Moultrie.
“Also his war fleet would have been sunk had they carried out their orders.”
His “war fleet” carried out their orders. Since they were not fired on by the Charleston batteries, they did not fire on them.
Neither was defensible from a motivated populace surrounding it.
His “war fleet” carried out their orders.
Well, considering their orders were to wait for Captain Mercer to take command of the task force and then reinforce Sumter, then yes, they did follow those orders, but everyone on the Confederate side believed that his showing up was just a formality and that these ships would soon be attacking the shore emplacements.
The force presented a credible threat, but unbeknownst to the Confederates, Lincoln had secretly left the pin in that hand grenade he threw at them.