People tend to think that events could have been easily predictable AFTER the outcome is clear. The certainty that people attribute to their predictions is much higher that it actually is. Also know as "Knew-it-all-along" phenomena.
Hindsight bias has been found to be more likely occur when the outcome of an event is negative rather than positive. This is a phenomenon consistent with the general tendency for people to pay more attention to negative outcomes of events. Hindsight bias is also affected by the severity of the negative outcome.
This has the ability to distort memories of what we believed/the probability we assigned to the outcome before the event has occurred.
This effect is so powerful that many experts think that true analysis of any decision can be done only before you know the outcome.