Caliban insists that the island is his but that Prospero took it from him by flattering Caliban into teaching him about the island and then betraying and enslaving him.
That is the reason for Caliban’s bad behavior.
Explanation:
After Miranda is fully awake, Prospero suggests that they converse with their servant Caliban, the son of Sycorax. Caliban appears at Prospero’s call and begins cursing.
Caliban insists that the island is his but that Prospero took it from him by flattering Caliban into teaching him about the island and then betraying and enslaving him.
Prospero lists Caliban’s shortcomings and describes his own good treatment of him, but Caliban answers with curses.
