Translation
I have seen slaves on horses and chieftains walking on the ground like slaves.
Paraphrase
I have seen the reversal of social norms; I have seen someone who was not a leader nor in a leadership role acting as if he were a big-time leader, demanding respect and honor, while people who were obvious leaders were not being treated with the respect they deserved.
Verses 5-7 Hint at the Word Vapor
This section, from verse 5 through verse 7, does not use the word “vapor” but it is repeatedly implied. Those things are like a vapor because A: they Accomplish nothing, S: there is nothing Special about them, even though people think they are special because they are different, and E: they are Endlessly frustrating to the people who have worked hard and done things the right way.