Trump doesn't have the authority to create new federal agencies, so he claims to have repurposed the authority of an existing one, retaining only the shell for appearances. I don't think that can possibly be constitutional - it entirely defeats the point of Congress having that authority, and is effectively a line-item veto if the law can say "this agency will exist for X purpose" and the president can simply ignore the "for X purpose" - but it doesn't matter if neither Congress nor the courts are willing to do anything about it.