Because the only acceptable answer in the GOP is that the Civil War was about Big Government!
It makes little difference what Nikki Haley actually believes. She simply cannot be trusted. She has shown herself adept at saying things that sound relatively sane one sentence, and then making appeals to the MAGA Right with the next.
She is either a fanatic herself, or (my belief) disingenuously willing to glibly court the fanatics.
And she is still arguably the least-worst of the folk at-all-possibly-getting-the-GOP-nomination-for-President .
https://www.politico.com/news/2023/12/27/haley-slavery-cause-of-civil-war-00133254
Haley declines to say slavery was cause of Civil War
The former South Carolina governor instead said it was a dispute over how ‘government was going to run.’
UPDATE:
Aaaand … Nikki Haley backtracks, admits that, yeah, slavery was the cause of the Civil War … which will doubtless draw more criticism from both sides.
She then deflects and says the person who asked the original question was a “Democratic plant” … which is altogether possible, but doesn’t address her inability to give the answer she knows is true in the first place.
So Haley is willing to tell the truth about the Civil War when forced to, but not when she isn’t. Got it.
https://www.forbes.com/sites/anafaguy/2023/12/28/nikki-haley-backtracks-on-civil-war-comments-says-of-course-slavery-was-the-cause/?sh=41062d6c622a
Nikki Haley Backtracks On Civil War Comments, Says ‘Of Course’ Slavery Was The Cause
In a town hall Wednesday, presidential contender Nikki Haley omitted slavery as a cause of the Civil War.