Frog in water: not subtle, not deadly, just refrain from drinking the water.
Frog in hot water Jumps out! So what, it's just a frog. Just don't drink the water.
Frog slowly emersed in water.....drawn slowly to a boil......slowly to its destruction.....will DIE!
Now you have a dead frog in water you still can't drink.
What is your point? Was it your clever plan to kill Iran? All 77,000,000 of them?