I've spoken before of how the Civil War could have gone several different directions.
Although I don't think that the South could have marched up North and enforced a slaveocracy on everyone, I don't think that it's impossible to imagine they could have chased the northern troops out of their territory and succeeded in secession.
At times, the Northern army had to contend with both large standing armies filled with experienced officers and troops as well as a brutal insurgency fighting on land it knew so well.
Then as now, the invading army did not know the lay of the land, did not understand who was their friend and foe and had to deal with corrupt army contractors that exhorted ungodly sums from the federal government to feed, clothe and equip the troops with the tools they needed to win the war.
Grant dealt with all this with a combination of cunning, bravery and brutality and ultimately oversaw Lee's surrender after taking the southern capital of Richmond, VA.
While Grant's predecessors all suffered embarrassing defeats and were suspected of sympathizing with the confederate army (most officers received their training in the South), he forced the south's surrender three times.
He won these fights through both intelligence and basic bravery. He anticipated the enemies moves, blocked supply lines and paths of retreat and would perform bold surprise attacks on the enemy's position.
The northern public loved Grant and ultimately promoted him to the presidency in one of the nation's darkest times.
Grant joined a large cast of former generals and military men to assume the presidency. George Washington, James Monroe, Zachary Taylor, Truman and Eisenhower among them.
I can't fault people for wanting generals to run the presidency. There's some logic to wanting people that know the price of war to be the only ones that can declare it.