Nice catch. What is Krypton known for? In fiction, it is Superman's weakness. Why would the creators of the Superman stories choose that element? It is a real element on the periodic table of elements.

Krypton is widely used in electronics like fluorescent lamps, and tubes. When a passage of electricity passes through a glass tube containing krypton, it emits a bluish-white light which is widely used in the flash lamp of high-speed photography. It is mixed with mercury to make the glow of bright greenish-blue light. In energy efficient fluorescent lamps, we used a mixture of krypton and argon to save power.

The world is conditioned to want a hero.... or a savior.... that uses physical strength to solve problems. The world lusts after the images of power and rejects the True Savior, who uses spiritual strength to save people. He speaks the word, and it is done, without needing to lift a finger. His word is spirit and it is life. And his nature is that of Light. So what is Krypton used for? Light. When the Light appears, darkness flees.