In Book 4 of The Odyssey, why is Helen's story and role so important?

Let us remember first and foremost that Helen was the
reason for the entire Trojan War, as her kidnap or escape with Paris, the young prince
of Troy, was what gave Meneleaus and his brother Agamemnon reason for attacking Troy and
starting one of the most famous battles in mythology. In Book 4, we focus on the fates
of other heroes from the Trojan War, and Helen is one of these. Seeing her happily
married to her original husband again, and what is more, celebrating the birth of her
children, perhaps foreshadows the happy ending that is in store for Odysseus and his
family when he finally makes it home and restores his
position.

Let us also focus on the particular story that
Helen offers about the father of Telemachus. As the characters feast in this book, Helen
and Menelaus tell Telemachus stories that celebrate the cunning and ingenuity of
Odysseus, and how this was used to win the battle. Helen's story in particular is
noteworthy because she tells Telemachus how his father disguised himself as a beggar to
infiltrate the walls of Troy and gain access to the city. Given the sheer number of
times in this book when Odysseus either disguises himself or pretends to be someone he
is not, witholding his identity, this story is key for preparing us for the character of
Odysseus and the kind of stratagems he employs.