Amazon as book publisher

Here is the latest:

In its most significant foray into publishing, Amazon has acquired world English rights to a self-published novel by a midwestern teenager called Legacy. The acquisition is the first for the e-tailer's newly launched publishing banner, AmazonEncore. Amazon is re-releasing the fantasy title, in hardcover, in August. The book, by Cayla Kluver, is part of a planned a trilogy–it was published under the banner Forsooth Books, founded by Kluver and her mother–and, according to Amazon, is the first in a currently unknown number of titles from AmazonEncore.

Economic theory predicts that if Amazon were to start publishing, it would publish nobodies rather than established star writers.  Can you explain why?