Question: What Reason Did the Confederacy have in believing they would have a quick victory in the Civil War.
The South had a better trained army at the beginning of the war which is indisputable given the results of the first major battle of the war. The South also had a more talented officers corps in the most important theatre of the war, the East. Much of the Union officer talent was confined to the Western theatre and would take years to emerge from the Union officers political environment. The South's best officers were already established in command. Stonewall Jackson, JEB Stuart, Longstreet were already in place at First Manasas. That's three of the Confederacy's four most important Generals already in place. Lee would emerge as their overall command (June 1, 1862) years before the Union would cycle through half a dozen disastrous and incompetent commanders, finally promoting Grant(March of 1864). When Grant eventually did come East, he brought Sheridan and Sherman with him.
These early Southern advantages were apparent in the first major battle of the war (First Battle of Bull Run) when the South routed Union forces which fled back to Washington dc in total disarray.
JEB Stuart pursued the Union army all the way to Alexandria without meeting any resistance. He was close enough to the city to see the Union's pickets. General Mcclellan who picked up the pieces of the Union Army after Bull Run is not treated kindly in history; but one thing he is given credit for is rebuilding the army of the Potomac after that catastrophe.
The Union's advantages at the onset of the war were economic, production, and population; all of which would take time to assert themselves in a war of attrition. If the South had kept the war from becoming such a war, they had advantages which they could use. The south could have won a political victory by sewing together victories and sapping the union's bifurcated will to wage the war. The South also could have won by capturing the Capital of DC and thus paralyzing the Union.
The Union did not have an advantage in officers or training of their army.
Why did the Confederacy think they would win easily? At first Bluster, but after Bull Run they had reason to believe the war would be a quick one. Many people believe Confederacy lost the Civil war at the battle of first Bull Run. The Union Troops were in a panicked unorganized flight back to DC. Reforming that mob into an army capable of defending the capital would take time. General Joe Johnston the confederate general in charge of the battle had used 1 army corps to defeat the Union that day. He had an entire army corps in reserve all formed up and ready to attack DC. The confederacy lost the civil war when General Joe Johnston decided not to pursue the union troops into the nearly undefended capitol and capture the union leadership. Stonewall Jackson wounded at Bull Run in the hand is said to have walked the camp seeking 200 men to follow him into Washington. He believed he could have ended the war with just 200 men (taken the Whitehouse ). I don't know about that, but with an entire Army Corps behind him, many believe the south could have won the entire war, in the very first major battle. This is a premise I first heard put forward by Col John Mosby, chief scout for General JEB Stuart in his autobiography. Col Mosby, an enlisted man at the beginning of the war, was at Bull Run that day, one of the second army Corps who weren't used.
The civil war was lost when the war became one of attrition. In such a war the Unions advantages became insurmountable.