The President can’t eliminate the department through executive order, it has to go through Congress. Of course, there’s lots of things happening right now that require congressional approval and congress is just sitting on their hands. Its setting up a massive battle where the courts say “you can’t do this” and Trump says “watch me” and then lower level people in the administration have to decide if they’re willing to defy court orders and potentially face criminal charges or not since they don’t have immunity like the President does. The President, of course, has a plan for this and is removing bureaucrats who might but the law above him and replacing them with unqualified loyalists.