"eclipsed public knowledge of all economists—better ones, he says— before Smith." Meaning of this sentence

Question

Even Smith’s critics do not deny the book’s immense influence. Murray Rothbard levels the criticism that The Wealth of Nations, in fact, eclipsed public knowledge of all economists—better ones, he says— before Smith.

I understand that the writer is saying that the Wealth of the Nations, eclipsed public knowledge of all economists, which means that the book overshadowed the past knowledge of all economists, which were better than Smith. But what is the use of "Before Smith" here ?

Does it mean that these economists were good before Smith emerged?

Answer 1

The Wealth of Nations, in fact, eclipsed public knowledge of all economists—better ones, he says— before Smith

This, to me, means that the fame of the book lead to the situation where these days the public is not aware of all economists that existed before Smith, and were even better than him. Or, simply put, neglects them.

I could phrase the above in perfect present too:

This, to me, means that the fame of the book has lead to the situation where for quite some time the public has not been aware of all economists that existed before Smith, and were even better than him. Or, simply put, has been neglecting them.

Answer 2

In this sentence, the phrase between the dashes—"better ones, he says"—is a parenthetical phrase: if you remove it, the sentence will still make sense. When I'm having trouble reading a sentence, I often try reading it again with the parenthetical phrases removed. Let's try it.

Your original sentence is:

Murray Rothbard levels the criticism that The Wealth of Nations, in fact, eclipsed public knowledge of all economists—better ones, he says—before Smith.

The bold phrases are parenthetical. Removing them leaves us with:

Murray Rothbard levels the criticism that The Wealth of Nations eclipsed public knowledge of all economists before Smith.

You might now be able to guess that the writer has left out some words, which the reader is expected to fill in:

Murray Rothbard levels the criticism that The Wealth of Nations eclipsed public knowledge of all economists [who came] before Smith.