Catastrophic events do end life and lots of it, but not all life. All critters that occupy an ecological niche may completely disappear with species higher up on the food chain being effected disproportionately.
So, as you can see, when conditions return to the new normal new species will evolve to replace those that went by the wayside.
The Dinosaurs ruled the Earth for over 100 million years then disappeared in the blink of an eon, to be replaced by the Mammals as top creature.
Unless, of course, the fossil evidence is a well-made deception, not of human making. (Just being thorough here.)