Order Regained

There are many ways to look at the conclusion of the Odyssey, but here's one that connects it to the Iliad:

The Trojan war begins after Paris, a guest in Menelaus's home, runs off with Helen, Menelaus's wife.  This is not good hospitality.

After the war, Agamemnon is killed by his wife, Clytemnestra, and her lover, Aegisthus.  Menelaus is Agamemnon's brother, and Helen is Clytemnestra's half sister. This is not good hospitality.

Finally, Odysseus kills the men hitting on his wife, Penelope, in their home.  Unlike her cousins, Helen and Clytemnestra, Penelope is true to her husband.

In a nutshell, then, Odysseus avenges all the inhospitable transgressions driving both the Iliad and Odyssey, with the suitors either symbolizing or paying the penance for all men and women who do the worst thing a guest or host can do: disrespecting the sanctity and boundaries of marriage.

This cycle is completed when Odysseus and Penelope return, together, to the "great rooted bed".