In 1945 there was a plan.
After the German forces surrendered there was a 4-party occupation (though not appropriate in Iran, I suggest) and a partial and pragmatic de-Nazification. Even though many escaped responsibility for their crimes against humanity, Germany quickly began to function again.

After a couple of years a competent liberal democrat government (die Bundesregeirung) was established in 75% of a new Germany within revised borders. In the east a communist government controlled the east – die Deutsche Demokratische Republic – (called “social democrat”) was imposed and was firmly controlled by the Soviet Union. It was autoctratic, corrupt, cruel and unjust, but it was better than anarchy.
The West received massive aid for reconstruction under the Marshall Plan and, though to a lesser extent, the East was also reconstructed.
For Iran, I see no plan. I hear no plan, nor any talk of a plan.
Libya. No plan – chaos. Iraq, no plan – chaos. Syria, no plan – chaos. Afghanistan, no plan – chaos.
The most sensible preparation for Iranian transition would be an international multi-lateral peace-keeping force under the UN. This approach worked reasonably well in the Balkans.
But Trump hates the UN and is seeking to replace it by his “Board of Peace”. He hates liberal democracy and favours US-friendly religious nationalist governments – which he wishes to see installed in UK and the individual countries of a broken up EU. Would he support the establishment of a secular liberal democracy – if that were the Iranians’ choice?
So how do we proceed?
Perhaps discussions about following up this suggestion of a UN-led transition might be a start?