I have read articles that this topic was discussed among the cabinet, and they were worried that if the South did nothing, they would be stuck with a useless fortress full of men with everyone wondering why the hell are they garrisoning the place?
They were concerned Lincoln would be made to look the fool and he would not have any leverage to force the South back in.
One might think that this would have allowed the South to remain separate and at peace, but this would be naive. Lincoln also sent a task force to Pensacola to seize Fort Pickens, and the Lieutenant he put in charge of one of his warships did everything he could to start the civil war in Pensacola.
Lincoln needed that war, and the South very much did not need it. The evidence indicates Lincoln was going to successfully provoke a war at some point, regardless of what the South did.
With control of 700 million per year at stake, there was going to be a confrontation.
If the South could have gotten recognition from Britain or France, and used their ships to carry the trade, it would have become unfeasible for Lincoln to stop them from maintaining their independence.
“Lincoln also sent a task force to Pensacola to seize Fort Pickens.”
Lincoln didn’t have to do that. Fort Pickens was already manned and equipped by Federal Troops. The issue was would Lincoln expend the forces necessary to defend Fort Pickens from an assault by Bragg’s forces.