Feynman is one of the best ever at explaining complicated concepts in ways almost everyone can understand. That is a very rare skill for the super intelligent to have.
Agreed on Feynman, but not necessarily on the generalization that it being a rare skill to simplify things. When you understand a thing so well, you can simplify it enough.
I think it also takes a certain humility of character (which can coexist with tremendous self-esteem and even ego; see Feinman, Richard for an example).
I know plenty of smart people that know a topic well and are still not great at simplifying it in a way that can be understood well by laymen. Separate skill imo