I didn't know Biden had removed the Houthis from the list of terror groups after Trump added them. I also didn't know that he'd been forbidding Israel from attacking them back after 200 Houthi attacks on Israel. Anyway Israel stopped listening.

Bombing the port infra would just end up as a massive self-own as it would hurt the whole world economically + the Houthis have other supply lines through places like western Yemen. Sure the civilians might starve but there's enough to keep the Houthi fighters going. Israel is doing this now but they're seeing it as the lesser of two Ls, as they want to take away the Houthis bargaining chip. Honestly it's not a great idea imo since Israel stands to lose economically by doing this but hey they're not known for considering long-term consequences.

Why would they need Iran's help?

Because they had extensive history with Iran as an illicit weapons broker which itself stems from the fact that Iran is a rogue state that has out of necessity developed extensive connections with illegal arms dealers and black market operators. Turkey, while not the most loved by western nations, is still much more legit than the likes of Iran. And yes the Saudis and Emiratis and Qataris bankroll Muslim terrorism but Iran's entire government is built around being a rogue state fighting the West ("Axis of Resistance"), so they can make deals with Russia, China, North Korea, and even America under the table. Let's put it this way, Iran's proxies have been incredibly successful: Hezbollah stalemated Israel in 2006, Assad's regime survived the Syrian Civil War, and the Houthis have managed to outlast the Saudi bombing campaign and are still outlasting American efforts to stop them now. Iran's actual military capability isn't that great, but their proxy militias and asymmetrical military doctrine have basically turned them into an incredibly resilient and disruptive machine.