How is it possible that the crowd, while listening to the orator during hate week, doesn't seem to notice that their enemy has been suddenly changed from eurasia to eastasia?

Referring to 1984 novel

The initial purpose of the formation of the party is to control the narrative and make people believe what the party want them to believe.

 However, by the end of the novel, the Party began to believe their own fake narrative and the people just blatantly believe what the party is telling them without using their logical approach to analyze who the true enemy is.