The Minister for Foreign Affairs of Australia, Alexander Downer, is so incredibly articulate. I wish I could one day speak like that.
Four things, as I see it, contribute for articulation of speech: one, is talent. People who have a talent to be articulate always come out that way, whatever their social stratus or education.
Two, is upbringing. If your parents are articulate you will grow up to speak like them and will continue to speak articulately forever. You got good bases.
Three, is education. Education does make people more articulate and also gives them the basis to be so. A person with a talent to be articulate but not enough education lacks wings to fly. It's like having muscle but no weight to lift. You need education to give substance and words to your talent for articulation.
Finally, four, is a clear mind. I have heard Mr Downer speaking to the National Press Club at lunch time and answering some questions for which he definitely had not a clear idea and his answers came out quite convoluted. When, on the other hand, he had a clear mind about the issues his articulate speech came out very impressive.