Albert Barnes Commentary Ecclesiastes 10:6-7

"folly is set in great dignity, and the rich sit in a low place. I have seen servants upon horses, and princes walking like servants upon the earth." — Ecclesiastes 10:6-7 (ASV)

The evil (Ecclesiastes 10:5) is here specified as that caprice of a king by which an unworthy favorite of humble origins is promoted to successive high positions, while a noble person is demoted or neglected.