Complex sentence: It was extremely difficult for the typical unknown author to get a publishing contract under these circumstances, and many'vanity publishers' sprang up to give these authors an alternative: essentially, they would publish any book in exchange for payment up front from the author.
Split into simpler sentences: It was extremely difficult for the typical unknown author to get a publishing contract under these circumstances. Therefore,'vanity publishers' sprang up to give these authors an alternative: essentially, they would publish any book in exchange for payment up front from the author.