Why police officers struggle when told, "The President ordered it"

Ah... I think this is correct.
It seems police officers have a bit of a bad habit. If they can't stand something, they tend to blow it out of proportion, twist things, and corner people.
Perhaps even the President knew about this habit. That might be why the President traveled all the way down to Busan to personally say, "Do it that way." It seems the police officers are flustered by those words.
This is why your police officers have high divorce rates or why their families aren't particularly harmonious.
The President understood the nature of the police.