Ironically, that's what makes 'explain like I'm 5' so useful - it takes away the assumptions people have in their heads and forces them to use simple language and explain things from first principles.
It's quite powerful really. Richard Feynman was famous for being to explain physics in a way a layman could understand. Neil deGrasse Tyson does the same and people love it.
Agreed. And the Challenger O-ring demonstration was a beautiful example of metaphor even if it wasn't correct. (Morton-Thiokol engineers had evidence that the O-rings didn't seal even at 75F and had been trying to stop launches PERIOD).
However, Feynman was also famous for "proof by intimidation" if you caught him out on something he didn't understand.
If instead you mean to use more common words and to make concepts relatable to everyday life - that usually works out pretty well in my experience. It's not an easy thing to do either for the "smart" leader.