Iran went hard out of the gate to disable significant portions of enemy military installations, and the US pulled a lot of materiel out in response. If the high value assets are moved out of reach, and Iran knows it, then there's fewer high value targets to hit.

But also, by lulling the enemy into a false sense of security, the enemy can be induced to engage in activities that otherwise they would not. Things like repair, recovery, or even potential cases of hardened underground facilities becoming activated and thus revealing themselves. Iran may be observing the enemy to see where they move their attention when the threat is reduced, which provides them with invaluable intelligence.