Huge beasts such as the dinosaur have never really become extinct. Mothra, a giant caterpillar who later becomes a moth, destroys Tokyo, and stars in the 1962 Japanese film named for him. Mothra is born, dies, and reborn regularly on classic movie channels. In Japan Mothra is one of the most popular films ever made. Mothra has survived the creation of more current scary creatures such as giant apes, extraterrestrial beings and swamp creatures. More than 30 years after his creation, Mothra still lives.
Question: The main subject of the passage is:
The reasons that fads do not endure
The lasting appeal of Mothra
The difficulty of marketing good horror movies
Old models for creatures are still used because making new monsters is expensive