Bill Essayli is the face of Trump’s immigration and fraud crackdown in Southern California. Defending his own family’s fraud case, with the ACLU’s help, pitted him against the office he now leads.

Mr. Musk dug into his companies’ budgets, preferring to cut too much rather than too little and to deal with the fallout later. Under Donald Trump, he is set to apply those tactics to the U.S. governm...