Sforno on Numbers 27:20/ספורנו על במדבר כ״ז:כ׳

1ונתתה מהודך עליו, you are to confer upon him some of the aura of your regal authority while you are still alive, so that the people will get into the habit of treating him with respect.

2למען ישמעו, the reason why you are to appoint him in full view of the people is so that the whole עדה, i.e. the Supreme Court, the leaders of the nation, will get into the habit of listening to what he has to say with reverence.