The universe is random, this asteroid was random, any cause and effect generalizations we as humans make to things beyond our control are just flaws in our psychological schemas. When you're a toddler, you go through this phase as your brain tries to understand the world around it. Well documented in psychology, for instance try explaining to a toddler that Jimmy pushed him on accident because Jimmy tripped over his shoelaces. He won't believe you.
It is more comfortable for our minds to believe that the world is going to end BECAUSE of something, a date, a calendar, a Bible chapter, than it is to believe that it could end at any moment, for no reason whatsoever.