When you are on the wrong side of history and development you do stupid and desperate things like attack the Union. The North did not need the South to wage a crushing war but the South needed everyone else. It couldn’t arm itself, protect its ports, feed its people or kill enough Yankees try as it may.
Lincoln sent a war fleet with orders to attack them first. Their choice was to attack the fort and prevent it's guns from being used on them when the War Fleet arrived, or sit there and do nothing until they came under fire by the Ships in the Harbor and the Cannons in the Fort.
Would you have sat there and waited for cannons to fire on you? No sane person would do this.
It couldn’t arm itself, protect its ports, feed its people or kill enough Yankees try as it may.
The 5.5 million people in the South could not reasonably stand against the 20 million people in the North if the North was determined to subjugate them. The numbers simply wouldn't work.
Nor could the 3 million Colonists have stood against the British Empire if King George III was determined to destroy them. King George III stopped the war after 15,000 casualties. Lincoln kept sending men into a meat grinder, and for no better purpose than to establish Washington DC supremacy over a people who wanted to be independent.
Nobody in the South believed anyone would be so fanatical as to kill so many people to stop them from having independence. Certainly Lincoln went far beyond what George III did.