Because
1. He had no choice and
2. He landed on her island 9 days after Charibdis broke up his ship and killed his men
Calypso wants Odysseus to stay with her on the island forever.
Odysseus met Calypso on her lush island of Ogygia.
Calypso
She loves Odysseus and wants to keep him on her island, but Zeus wants her to let Odysseus go.
Calypso
Calypso is the last one to keep Odysseus against his will on her island. The name of the island Calypso kept Odysseus on was Ogygia.
Calypso offers to make Odysseus immortal and forever young if he will stay with her on her island. Odysseus respectfully refuses her offer.
Odysseus spent seven years on the island of Ogygia with the nymph Calypso.
Hermes tells Calypso to let Odysseus go.
Calypso does.
Calypso.
Calypso