“there was no reason why any ships would sail the extra 800 miles to Charleston to trade there.”
Yes, there is. When the owner of the cargo on that ship, pays the shipping agent to ship the cargo to Charleston.
What would that cargo have been? Railroad iron? Not worth it because of the tariffs. Cost more to ship it from Europe than it was to buy it from Pennsylvania.
Oh wait! I think I see what's going on here!