When the St. Louis Cardinals won the World Series many people said they knew from the beginning that the Cardinals would be the World Champs. This belief that outcomes could have been predicted earlier is an example of a cognitive bias called.

This belief that outcomes could have been predicted earlier is an example of a cognitive bias called Hindsight bias.

Explanation:

Hindsight bias is defined as the tendency in people to overestimate their own ability to predict an outcome in the future, that has nearly no chance of being predicted correctly. It is an extensively used term in psychology and fits the description given by question completely.

This is quite common and can be explained better by an example like when an outcome happens and a person says "I Knew It", thus in this case, creating a tendency in them that they could've predicted the outcome which is simply chance and not a prediction at all.