Lincoln didn’t start the WBTS.
The Confederates first committed an act if war, and there may have resulted a war from it whereby Lincoln got Sumter back, he was compensated, and/or southern states were proportionately punished. The war we got was not that war. Sumter did not permit Lincoln to conquer the Confederacy.
SCOTUS, of all things, placed the official start of the war at the North’s blockade.