Hindsight bias is a common psychological bias that all humans are prone to, in addition to others that make what you're talking about happen so often.

From Wikipedia: "Hindsight bias, also known as the knew-it-all-along phenomenon or creeping determinism, is the common tendency for people to perceive past events as having been more predictable than they actually were. People often believe that after an event has occurred, they would have predicted or perhaps even would have known with a high degree of certainty what the outcome of the event would have been before the event occurred."