The Iranian people overthrow their government and establish what they want?
My point is that an outside force coming in will help the current regime and/or the ideas behind it. Even if the current regime falls, democratic or pro-Western ideas in Iran will be seen as aligned with the invading force and rejected by many people who might otherwise be open to them.
Is there anyone who likes being invaded by a foreign power, ever?
The British in 1688 (Glorious Revolution, when they were invaded by the Dutch).