N2, not referring to people posting here, but there are things difficult to communicate and things that don’t make any sense.
Great researchers are not always great teachers (most of the time for laziness, otherwise they would not necessarily great, but at least half-decent), but great researchers have clear ideas in their minds.
And there are people able to explain things much more complicated (in absolute terms) than training (for instance, grad courses in some hard science). Of course, the audience has to be of decent subject-specific knowledge.
I always liked how Charlie was able to communicate. I’m sure he was keeping more advanced (and maybe not fully formed) concepts for smaller audiences.