Complex sentence: By 1974, the ratings had sunk low, David Cassidy finally had had enough of playing Keith Partridge, and one of his teenage fans had died of heart failure from injuries sustained while attending one of his concerts.
Split into simpler sentences: By 1974, the ratings had dropped and David Cassidy finally had had enough of playing Keith Partridge. One of his teenage fans had died of heart failure from injuries sustained while attending one of his concerts.