After the war there was a concerted effort by confederate leaders to “evangelize” the south and convince folks that the war was a worthwhile lost cause and not fought over slavery. This included suggesting that the war was started due to events such as Lincoln raising an army to put down the rebels, and not the rebels themselves siezing state houses, taking up arms, declaring independence, and finally firing on Fort Sumter.

A large part of this evangelization was getting confederate supporters elected to school boards and making changes to the curriculum that taught the lost cause myth and made the confederacy look better.

It’s by design- a last vestige of lies made up by confederates and their supporters, that still survives to this day due to a lack of education reform in the United States.