A civil war is the nastiest way to get a good result. The United States hasn’t faced a succession crisis since we settled that ugly business at Appomattox in 1865, and no one to the left of the Ku Klux Klan has since advocated we bring back slavery. Getting there cost 600,000 American lives, but obviously they were not lost in vain.
The English Civil War established parliamentary supremacy over the King, in a way that no nice law ever could. Maybe that’s what Thomas Jefferson meant when he wrote that “The tree of liberty must be refreshed from time to time with the blood of patriots and tyrants.”
That’s not to say that every civil war has a happy ending. China has suffered more civil strife in its long history than modern Italy has had governments