The first thing I did not know was that both Fort Sumter and Moultrie were still active coastal defence installations during World War II and that coastal batteries were built inside both of them to defend Charleston Harbor from German U-boats.
The second thing I learned was being amazed at looking out to sea and seeing the big cargo container ships sitting on the horizon waiting to enter port to unload.
The third thing I was impressed with was exactly just how narrow the shipping channel between Fort Moultrie and Fort Sumter really was and just how much that Fort Sumter commanded that channel and dominated Charleston Harbor. Either one of those two Forts could have bottled up Charleston Harbor but Sumter had one advantage, it couldn't be approached by a land force. It could only be approached by boat which gave the defenders of Fort Sumter the advantage in repelling and attack.
It is no wonder that the people of South Carolina would have felt threatened by the occupation of Fort Sumter. Had Anderson stayed in Fort Moultrie the people of Charleston would not have felt as threaten as they would have by Fort Sumter occupation, because of the Land connection.
But for all of that, in my opinion, the occupation of Fort Sumter was the validation of all of the suspecions that had built up in the southern people all across the southern states after John Brown's raid. That is why it was such a flash point and touched such a nerve with the next 6 states to seceed when the "Star of the West" tried to reenforce Andersons Garrison.