The people didnt switch directly.It was a slow movement in education which was mainly funded by a certain group of Confederate women called The United Daughters of the Confederacy.This was an wxtremely powerful and influential group made up of extremely rich and connected women which made a great effort to oush the propaganda of the “Lost Cause”.This was made possible by a total lack of supervision by the part of the central goverment because it deemed the initial plans of keeping the troops and a tight leash on the South as too expensive and just bailed out leaving them to their own devices. The Daughters,as a group,publicly announced they were just concerned women who wanted to honor the fallen and the war,and went this way with a lot of charity and building of memorials.But they also funded lobbyying about the writing of history books,laws about memorials of war criminals,they made awards for Confederate veterans and even provided scholarships for Confederate supporters(and you guess most of these were history scholarships),etc...

This group in particular,is the reason that the Confederate worshipping was veiled in mysticism and an affair of a lost cause for freedom.(Total hogwash)

And many politicians(many ex confederates) pushed this narrative hard,in order to keep the Confederacy alive in memories and its ideals alive,in order to continue in the best of their efforts to keep the romanticized idea of slavery and segregation and oppression alive.

This was a tactic that took 1 or 2 generations to take place,it wasnt immediate and it has been so implanted that it still continues today,without the need for fu ding because of the feedback loop it created

So this new comment is in here to add more context to my previous content and add some more specficities to the narrative of the rise of the “Lost Cause” propaganda in Southern tradition and education that came as a result of hard lobbying from mainly 2 organizations.

The United Daughters of the Confederacy and Sons of Confederate Veterans.But the most influential in education of those 2 groups was the Daughters.And this was a long,looong process that took a generation or two to take place,as the Lost Cause was mainly a tactic to continue Confederate worshipping,withoutgoing into slavery rants.

The United Daughters of the Confederacy was founded in Nashville,around 1894 by Caroline Meriwether Goodlett and Anna Davenport Raines.They were clearly in there for the propaganda,as their main focus was the reframing of the American Civil War to show the Confederacy in a positive light,as to keep the tradition alive for the future generations.Their stated and written intention was to “tell of the glorious fight against the greatest odds a nation ever faced, that their hallowed memory should never die." This clearly shows they completely embraced the “Lost Cause” rhetoric and would go on to be the main push for this propaganda point in education.

As an organization it first started as a charity of sorts,as shown by them funding,alongside Sons of the Confederate,several war memorials and charities for widows and orphans of the war.

2 year later,this propaganda push in education reached full form with the establishment of The Children of the Confederacy.By getting so involved with children support and education they easily pushed Confederate propaganda towards the weakest of society. Children were and still are to this day as we speak taught "Catechism on the History of the Confederate States of America, 1861-1865",which says that Northerners did away with slavery because the climate was unsuitable, that they had no intention of ever paying the South for its slaves after abolition, that slaves in the South were faithful to their owners, who were caring and gentle people: cruel slave owners existed only in the North.(This is word per word what the book states)

They also have an award of their own,called “The Southern Cross of Honor” ,a commemorative medal created for members of the United Confederate Veterans.This was proposed by the daughter of Howell Coob,a confederate politician,the President of their Provisional Congress during wartime and also a Major General in the Confederate Army.And the first person to be awarded that medal was her husband.

Her father is the guy that said “You cannot make soldiers of slaves, or slaves of soldiers. The day you make a soldier of them is the beginning of the end of the Revolution. And if slaves seem good soldiers, then our whole theory of slavery is wrong." in response to the idea of conscripting slaves into the Confederate Army once defeat was near,in a upstanding of the Confederate as a slave state create on the basis of slavery

At the 1907 General Convention, Caroline Meriwether Goodlett spoke of the shift in the UDC's focus. As monuments were erected, she "sat by ... thinking that the monument fever would abate". She believed that "the most thoughtful and best educated women" in the organization should have realized that the "grandest monument (they) could build in the South would be an educated motherhood". Basically cementing the idea that memorials were just a small part of the propaganda process and it should be focused on education.

And let it be known this group also promoted a different book later in 1913. “The Ku Klux Klan, or The Invisible Empire” was a book written by a member of the United Daughters,Laura Rose.And through some heavy lobbying became a supplementary reader for Souther Schools and they later even funded and made a Klan memorial in Concord,California.

Their involvement in education and inf shaping Southern education can be seen that their members had achieved some of the highest echelons of Southern Education.Like the the first Dean of Women at Montana State College being part of UDC,or president of the Texas State Historical Association for 10 years steaight was an UDC member(1915 to 1925).

So to answer your question,the Lost Cause wasnt meant tk be taken seriously by ex-Confederates.It was to add longevitiy to its praise for the generations to come,and continue its white supremacist views,while also not directly supporting slavery,and it took generations to take full effect and infiltration of education by policy or by educators themselves,resulting in the Modern Day with these groups still alove and kicking and now their systems have created a feedback loop of Confederate propaganda which instill a Confederate indentity to Southeners

Sources

Caroline E. Janney (2012). Burying the dead but not the past : Ladies' Memorial Associations and the lost cause

Enduring Legacy: Rhetoric and Ritual of the Lost Cause By W. Stuart Towns(2012)

Mildred Lewis Rutherford (1916) What the South may claim

Kristina DuRocher (2011) Raising racists : the socialization of white children in the Jim Crow South

Also to add is nice to check the Minutes of the Annual Meetings of the UDC,which are avaible for free to just bask at their propaganda