Why does Mr. Oakhust use the deuce of clubs? What meaning does it have?

The answer is: Change their predictions.

Explanation:

As students read and learn more about a conflict in a story, they tend to make predictions about the next steps or stages that could be encountered or read: they expect certain situations to arise based on previous knowledge. Since expectations or predictions don’t often come to pass as expected, students may have to mentally revise or change their predictions or expectations as they read and get more information.