For those of use Harpoon fans, using SM against surface targets is not new. Standard ARM (AGM-78) does a nice job.
True its a small warhead but if you shread the Radar system on a surface combatant you have blinded it and it becomes pretty much a target for anything else you might want to send its way.
Local control Air / Missile defense is generally not all that good.
You pop off 5-10 of them. You do so at less than max range so their fuel gets added to the fires started by the supersonic impact and warhead.
The enemy ship loses it’s sensors and the crew comes out on deck to fight the fires. Thats when the follow-on strike with Harpoons hits.