They didn't need to fire hundreds of them now because they already dismantled those radars. They were firing more at that time to penetrate the system and destroy those radars and everything around. Now there are 17 radars, and American assets that were coming between Israel and Iran at that time have already been destroyed, so they don't need more weapons. They just need a few of them.
They knew that 90% of those weapons would be blocked and destroyed by the defense systems. Now that the defense systems are not working, they don't need to fire that extra 90% just to allow 10% to penetrate the defenses.