Why did such a small percentage of southerns have large slave holding

Economic inequality

Explanation:

In short, the South was an unequal society in which wealth was concentrated in the hands of a few plantation families and merchant families. So, most people could not afford slave operations.

most of the knowledge we have of the conflict comes from roman-jewish scholar titus flavius josephus, who first fought in the revolt against the romans, but was then kept by future emperor vespasian as a slave and interpreter.