>It was also a bad idea then. They could never have effected regime change

They could have if they'd done what Israel wanted and destroyed all the oil infrastructure. The IRGC is heavily dependent on oil revenue for funding its oppressive apparatus; without it hundreds of thousands of militia would go without pay and eventually desert. For whatever reason Trump didn't want to do this; likely not for humanitarian reasons given his nature, but for some reason he seemed to really care what Turkey and Pakistan think, both of whom don't want to be flooded with refugees.

> if they'd done what Israel wanted and destroyed all the oil infrastructure.

That would have worked. But it is still a stupid idea if you don't cripple and destroy Iran's military capability first as Iran would have also retaliated and destroyed all its Arab neighbour's oil infrastructure too, plunging the world into an economic depression because of the energy crisis it would cause - The Iran War Is Destroying Something More Valuable Than Oil - https://houseofsaud.com/iran-war-refinery-crisis-saudi-aramc...