With the relief on the way and Lincoln figuring it would be fired on----the Confederates decided to fire on the fort. Lincoln called for his 90 day wonders and the war was on---He got his wish--Southern fire.
This is the second reference to 90 day wonders in this thread. Do you know why 90 days, why 75,000? Hint it involves the Constitution, Congress, and the laws passed by congress. Look at what happened when Congress got back in session.
As for this whole thread talk about missing the forest for a tree. Someone figures out the the U.S. would be economically damaged by the south seceding, real sherlock Holmes here. It was more than economic damage though. Set the precedent of just letting states leave because they use force and don't like the result of an election? The Union wouldn't survive, hello Balkanized North America. States unilaterally seceding without the input of the whole nation establishes death for the republic. So yeah when those South Carolina fellas fired on U.S. troops Lincoln reacted the same way Jackson would have, or how Washington did. To focus on the economic damage while ignoring the damage to the nation is like focusing on a a scraped knee while the kid is concussed. The U.S. did have a moral reason to keep the states rebelling by force in and that is survival of the republic. That is why Lincoln and the U.S. reacted to what the rebelling states started.