Complex sentence: During the 1990s Seagull had a cooperative advertising program with independent publisher Bookcraft, but when Deseret Book bought out Bookcraft in 1999 Seagull began to worry that Deseret Book would give preferential treatment to its own retail stores.
Split into simpler sentences: During the 1990s Seagull had a cooperative advertising program with independent publisher Bookcraft. When Deseret Book bought out Bookcraft in 1999, Seagull began to worry that Deseret Book would give preferential treatment to its own retail stores.