Complex sentence: Instead, Spiegel suspected Wilbur of having publicized Mason's case for financial gain; according to Spiegel, Wilbur responded to his assertion that Mason wasn't a multiple by saying the publisher wouldn't publish the book unless they said she was.
Split into simpler sentences: Instead, Spiegel suspected Wilbur of having publicized Mason's case for financial gain. Spiegel confronted Wilbur, who responded that the publisher wouldn't publish the book unless they said she was.