As the story of Exodus begins, we learn that a new Pharaoh appeared on the scene, who “did not know Joseph” (Exodus 1:8). This is when the trouble between the Israelites and Egyptians begins: this not knowing eventually becomes Pharaoh’s destruction.
In “Rereading the Plagues,” David Silber writes:
Pharaoh’s “not knowing” carries with it a sense of ingratitude, as Joseph was the savior of his nation; it also suggests callousness and a lack of sensitivity, and the Torah implies that it is not just an intellectual lapse but a moral deficiency.
— p.56, Go Forth and Learn: A Passover Haggadah. Phil., PA: JPS, 2011.