Complex sentence: The modestly successful show was put on hiatus in early 1978, being replaced by "The Incredible Hulk"; it came back during the summer to air its final 10 episodes before ultimately being canceled that August because of low ratings.
Split into simpler sentences: The modestly successful show was put on hiatus in early 1978, its time slot taken by "The Incredible Hulk". It came back during the summer to air its final 10 episodes before ultimately being canceled that August due to low ratings.