Why are space telescopes the only telescopes that can view celestial star explosions?

Not true. There was a supernova that was visible to the naked eye a few years ago. Telkescopes on the ground pick up plenty of novas. However, a space telescope is outside the dirt, fog, and fuzziness created by our atmosphere, and are able to see much better. They can also see infrared and ultraviolet light, which generally don't get through the atmosphere. but novas and supernovas have long been studied from the ground.