Complex sentence: During their marriage he attempted to burn her parents' house down (it is reputed this was to persuade Drumm to buy life insurance), claimed he had had a heart attack and cancer, and tried to murder her in a car crash.
Split into simpler sentences: During their marriage he attempted to burn her parents' house down, perhaps in order to persuade Drumm to buy life insurance. He also claimed he had had a heart attack and cancer, and tried to murder her in a car crash.