The expressiveness of gestures
Human beings are developed to be relational, or to be interactive with their peers, so it is quite normal to communicate with every means at their disposal, not only with their voice, but also with all gestures of the body. This type of communication is inherent within us so that we are able to sense the attitude of a person without them uttering a single syllable.
Some people gesticulate far more obviously than others, but every time someone feels the need to express a concept which they believe in they will instinctively begin to gesticulate with the whole body, in an attempt to implement fully their ideas.
This type of communication, also present in singers, is totally instinctive and is devoid of conscious control.
Being able to recognize excellent communication abilities in others does not mean knowing how to reproduce it correctly. When observing a charismatic person speaking, you cannot learn their "secrets", or even copy them, worsening your own ability. The caller is immediately aware of the imbalance between the verbal and the paraverbal message: they will not unconsciously accept it, justifying the idea with an unidentified "sixth sense". It is not important the message that you think you have sent, but what was actually recognized by the other person!
You should not think that you can learn how to communicate properly or how to improve your own ability a speaker by following a simply course in public speaking: you must address all these issues, as you have understood are unconscious, therefore not directly controlled by conscious thought.