An attempt to answer the OP with a non-racist but completely amoral view of history:
Segregation existed in some degree all over the country, but why and how was different to a degree. In the states that had been a part of the Confederacy much of Jim Crow was a backlash against Reconstruction, when white people were suddenly presented with black elected officials (their capability or qualifications for office were often unimpeachable but when you have always seen blacks as slaves or less-than-citizens it was jarring) and their economies are devastated.
Then no matter what the South did they couldn’t win for losing. In 1866 cotton prices were good- thirty-cents a pound for top quality- and that same year the boll weevil does record damage in Georgia and Alabama while Louisiana and Mississippi have record floods. After 1867 the cotton market stagnates and with the opening of the Suez Canal the cotton market declines far and fast, so the south is suffering. Some have gotten out of the agricultural endeavors and begun to make progress: just to use two famous examples Nathan Bedford Forrest (a self made multimillionaire before the war and broke when it ended) had slowly begun to regrow his fortune with railroads and public works contracting, Jefferson Davis (his plantations confiscated at the end of the war) had begun regrowing his through presidency and partial ownership of a successful life insurance company, and in 1873- BLAM. The other shoe drops and it’s a steel toed boot- Forrest and Davis go almost overnight back to being broke and so do millions of other people. Unlike the Civil War the Panic of 1873 wipes out millions and millions of non southerners as well, BUT for the south it’s becoming almost a dark comedy of “WTF is going to happen to us now? We go back to cotton farming- we lose our shirts. We get out of cotton farming go into business and industry- we lose our shirts. WTF?!”
But meanwhile blacks are generally doing better than ever before. This is not to say they’re eating bon-bons and singing and loafing and getting checks from the carpetbaggers, they’re working their asses off like everyone else for low pay and terrible cotton prices, BUT they are doing as well as most whites and they are enjoying freedoms they have never had before- will soon not have anymore- that allow them to vote, run for office, attend school, bank, and other things that white people all took for granted. Certainly most blacks, like most whites, are in poverty or spitting distance therefrom, but to the white southerners- many of whom had not been impoverished before the war- and nostalgia for that era growing daily*- it looks like the blacks are not in the same boat but dancing on the shore.
The KKK had been founded in 1866 (or 1867- an argument can be made for either) and other secret militia-groups (some not as terrorist in nature as the KKK and some of which made the KKK look like Boy Scouts) are formed and within a few years are defeated through legislation and sometimes military engagements; their power was pretty much broken by the mid 1870s. Again- this is an amoral judgment of history- but while many southerners even at the time denounced the KKK (including Forrest) many also saw its collapse as yet another reminder they were occupied and powerless as well as penniless.
Then came the fustercluck election of 1876. Makes Gore/Bush 2000 look like a friendly debate over a checkers game- results in the Compromise of 1877 whereby the Southern Democrats agree to hand the election to Republican Hayes in exchange for which Reconstruction ends, the troops go home, the war is over, the South doesn’t need the North to oversee its elections, we’ll handle it from here, thank you very much. Suddenly the south is again completely under the rule of its own elected officials again and there are no troops to enforce anything.
To many southerners- again this is an amoral judgment- it was payback time. The blacks become the scapegoats: every single thing that is bad and has gone wrong in the past 20 years is because of them and they’re going to get back to where they once belonged. They may have voted in 1876, but they’re not voting in 1878 if it takes enforcing every poll tax, literacy test, and obscure ruling from 1787 to the present and a few we just reinterpreted. About those schools and the black judges and all that- hope you enjoyed them, because it’s over. And while it’s impossible to legally or even practically re-institute slavery, the southern politicians did everything they could to turn back the clock to 1861 and they ran on the tickets of undoing all the damage done our pride and our land by the presence of the Yankees and the elevation of the blacks to your equals and neighbors. By 1880 most blacks were disenfranchised and it would get worse for several more years.
1896- Plessy v. Ferguson- separate but equal is allowed. Let’s see- you got a school with a door and some windows, we got a school with a door and some windows- never mind that ours has got a roof and yours has a piece of canvas and the windows have no glass in them, it looks equal to me. And so it goes.
So by 1925- the date you chose for the OP- this is how it’s been for as long as most people have been cognizant. Only those over 60 can really remember a different time all that well and those over 60 are mostly out of the work force. It’s become ‘how we do things’. (Again, this is in the south; in many non southern states there is also segregation and it has nothing to do with Reconstruction.}
*Oscar Wilde 1882: "The nostalgia for the antebellum era is so extreme that to compliment the beauty of a full moon will cue the response ‘yes, the moon is lovely… but you should have seen it before the war’.