The end of the world as we know it is an idea we're simultaneously petrified of and completely fascinated by. We see it constantly in fiction. The zombie apocalypse is one of the hottest ideas in fiction today, being exploited on TV constantly. Man-made and natural disaster films keep selling, and people keep craving more.
Maybe it's dissatisfaction with our own world, or just the same fixation we have on our own mortality, that fuels us to obsess over the mortality of our Earth. Regardless of the reason, it's been inspiring songwriters for ages, and it's produced some of the most blistering metal songs and inspiring anthems.