They shelled Ft. Sumter because Lincoln sent a fleet of Warships to attack them. You just don't hear about it in your history lessons because it doesn't support the narrative that the Confederates attacked first.
Lincoln swung first, but the Confederates actually connected first.
If the South had not shelled Fort Sumter, there would have been a good chance there would not have been war.
This is incorrect. Lincoln needed a war and he was going to cause a war one way or the other. At the very moment the fleet of warships was sailing to Charleston to sweep away all resistance, he had a warship sailing to Ft. Pickens in Pensacola with orders to start a war there. If it hadn't happened in Charleston, it was going to happen in Pensacola.
The South was paying 3/4ths of all Federal revenues and more than that, an independent South was a grave threat to the financial interests of Lincoln's backers. There was going to be a war because it was the only way the Crony Capitalists backing Lincoln were going to be able to come out of the thing with their assets.
But too many Southerners thought they were Napoleon, Genghis and Alexander in overalls, and they wanted war.
Why would they want war? With Independence they achieved an immediate 100 million dollars per year boost in income due to the vast bulk of New York trade shifting to the South.
You may not get this, but virtually all of the export shipping from the US was carrying Southern products. The South accounted for 3/4ths of all the export revenue the nation earned, and it was only because of oppressive and jiggered laws that the return trade went through New York.
Independence meant that the South could ship product to Europe and the return imports would come back directly to Southern ports instead of going through the Federal tax collection and middlemen in New York.
The South was going to make a *LOT* of extra money from being independent, but of course the New York power brokers were going to lose a huge amount of money in the process.
That's why there was a war. One way or the other, the Crony Capitalists in collusion with Washington DC was going to have a war they badly needed to stop the South from becoming economically independent of their control.
Economics are a wonderful thing, but Gen Beauregard and the others there were excited as they could be to fire that shot.
And the South did not want to stay in because they had the upper hand in Congress and were losing it as more Free states came in.
That is why Lee and others did not want to start shooting, but the fire breathers did. They thought the South could easily beat the North, and that the money would flow to them, to keep up their “peculiar” way of life.
And the ships sailing to Fort Sumter were to resupply Sumter, not start a war. Lincoln did not give them orders to fire.