Why do people think that the world is ending soon? The human species is resilient enough to make it through?

Between WWI and WWII there has been close to 100 million deaths and the Bubonic Plague taking over 150 million lives. These are just two of the more devastating examples of how we as a species are hard as nails and won't go down. Our population has skyrocketed over the past few centuries and considering how resourceful we are I doubt we are going to perish anytime soon.