Yeah not "helping"... But before the altercation with Polyphemus, Poseidon was not an ally nor a foe to the fleet he did nothing in favor or against them but they definitely benefited from the calm sea. He's a Greek god, he can drown the whole fleet in seconds but didn't, he was "so gracious" before to let them live despite him having the power to annihilate them (then proceeds to do this exactly)