After all these months of discussing this, you post this thing that makes me believe you do not understand what happened?
Captain Mercer was to take command of the fleet and direct it's resources. I think i've even seen an order to that effect sometime back.
The ships that arrived in Charleston were expecting Captain Mercer to sail the Powhatan into their midst, and take charge of the operation. They were instructed to wait for his arrival.
Captain Mercer wasn't coming. Lincoln had made certain he wasn't coming, but also made certain that nobody outside of him, Lieutenant Porter, and that guy in the shipyard, knew he wasn't coming.
The Confederates thought he was coming. The flotilla of ships thought he was coming. They weren't going to do anything until he arrived.
Do you now grasp the situation?
Their orders only allowed the use of force to aid the resupply effort, which never took place.
My recollection is that their orders were conditional on Sumter not having fallen.
Without them showing up, there likely would have been no attack. That is the impression you get from reading Beauregard's messages.
Do you now grasp the situation?
Do you understand in a naval formation that the senior officer afloat is to Command? Mercer not being there means that the next senior officer assumes command of the formation and carries out the orders for the mission. Since Fox did not order the supply mission to start, the naval forces stood by.