Complex sentence: Attendance was fueled by the star wattage provided by Melina Mercouri in the title role (who was nominated for a Tony Award for her performance and had starred in the film), which managed to overcome the mostly lukewarm to negative reviews.
Split into simpler sentences: Attendance was fueled by the star wattage provided by Melina Mercouri, who was nominated for a Tony Award, in the title role. She had starred in the film, which managed to overcome the mostly lukewarm to negative reviews.