Do you think Trump has a plan - he seems to blow with the wind and experts on the media seem not to know what he's up to?
I think he was intending to sit on the sidelines and let both sides get on with it, and then saw how well it seemed to be going for Israel and now wants a bit of the action/glory.
The fall of the regime would please the majority of the Iranian public but I doubt if the majority want the government to 'surrender'.
I have a feeling that the Ayatollah might just call Trump's bluff and sit tight - they have survived 46 years.