Iran has no way to “obliterate half of Israel’s civilian population”. The reason why they haven’t launched a full scale war is because they know it is Iran that would be leveled not Israel. Not only does Israel have nuclear weapons but also has the United States as an ally.
The US has the most powerful military that has ever existed in the history of the world. Many nations talk big against the US. The US usually responds like it does with the Houthis.. using a tiny tiny amount of its capabilities to stop the threat. And even when the US goes to war it still fights with one hand behind its back. The US, unrestrained, could obliterate everyone in Iran in about an hour.