Why is Poseidon angry?

In both the Iliad and the Odyssey it isn’t overtly clear as to how Poseidon’s grudge against Odysseus originated. One of the strongest theories about how it began is because Poseidon is said to have favored the Trojans during the Trojan War, and since Odysseus was the hero that turned the tide in that war in favor of the Greeks, Poseidon wasn’t happy. Almost immediately though, they’re shipwrecked on the magical island where the Cyclops, or one-eyed giant, Polyphemus, Poseidon’s son, lives. Odessey kills him .  This is why Poseidon can punish Odysseus, but it’s also why the other Olympian gods, the major Greek gods who are said to reside on Mount Olympus, prevent Poseidon from killing Odysseus. To exact this ultimate punishment would be to suggest that only partiality matters and that no public rules, norms, values, or laws exist.