>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.