He's going to get the trillion dollar contract to replace government vehicles with self-driving Tesla cars. They won't work right and they'll catch fire and kill government workers, but that never stopped him.
He's also going to get his other companies massive government contracts. eg SpaceX to take over many facets of NASA. Mission to Mars, US tax payers will pay for it, Musk and pals will make billions.
That is until the Trump-Musk relationship sours. But he's going to be a trillionaire off of US payer money and Trump will be getting kickbacks.