Complex sentence: By the late 1960s the popularity of Tony Curtis as a matinee idol was beginning to wane however the film was considered topical as during the previous few years films and pop music which related to California beach culture, had proved very popular.
Split into simpler sentences: By the late 1960s the popularity of Tony Curtis as a matinee idol was beginning to wane. However, the film was considered topical as during the previous few years films and pop music which related to California beach culture, had proved very popular.