Because the POTUS is the chief executive. His literal job is to manage the executive branch of the government. Unless his policies go against the law, there i

Because the POTUS is the chief executive. His literal job is to manage the executive branch of the government. Unless his policies go against the law, there isn't anyone who can legally dispute his policies for the executive. And if he does something illegal, the Senate can impeach him. At least, so goes the theory.