The Houthi threat was in and around the red sea. Iran’s naval reach is limited to with whatever it is they call a “Navy” in the Gulf of Oman. Almost on other side of the Arabian peninsula. Also the Houthis got pummeled once the U.S showed up. The U.S didn’t even continue a sustained campaign to wipe them out. Something it is more than capable of doing with just a single carrier group. That’s not even counting the Saudis getting involved.

Because they're dumb and caught up in the propaganda. They think war is a video game and it's normal for a country to just bomb a country.