There is never a good time to do what has to be done. The next president after Trump will be a democrat like Obama who wants to hold hands and sit and talk them out of their fanaticism.
The next democrat president will just give them the bomb.
Trump is doing what has to be done instead of leaving it for the future. Sanctions are crushing the mullahs so hard and are such a threat to their control, that they prefer to have bombs dropped on their country instead.
This is exactly why U.S. military action should be RARE, not as pathetically commonplace it has become.
Our system of government with its frequent transitions of power is simply not set up to engage in the kind of long-term idiocy that has become the norm in these foreign entanglements.
Further complicating all this is that we allow foreign interests to lobby our government buy our political leaders, so our "foreign/military interests" usually coincide with the interests of whichever country is more successful in buying Congress and the White House.