Answer: Leaders will highlight the positives of every situation to make themselves seem competent.
Card-stacking is a propaganda technique. It refers to the manipulation of an audience by altering their perception on an issue by emphasizing one side and repressing another one. This is done through speeches, media bias or censorship. It is used by political candidates to discredit their opponents and make themselves seem more competent.
In this example, Squealer is trying to make Napoleon look cunning and clever because he was not "fooled" by Frederick into accepting a cheque. However, the animals do not know that a cheque is just as good as money and that Napoleon is actually ignorant, not capable.
