Complex sentence: The group entered a sharp decline after the failed prophecies and experienced another schism as a small part of the group broke away from Chen after being persecuted by Chen, and renounced Chen's esoteric claims and pseudoscientific prophecies in an advertisement on the local newspaper.
Split into simpler sentences: The group entered a sharp decline after the failed prophecies and experienced another schism as a small part of the group broke away from Chen after being persecuted by Chen. They renounced Chen's esoteric claims and pseudoscientific prophecies in an advertisement on the local newspaper.