Great Writers

Sometimes, I wonder how the great writers like Shakespeare, Chaucer, Cervantes, Jane Austin, Charles Dickens, Tolstoy, and all the others managed to write at such a high level without being in writing groups. How did they do it--write beautifully, grammatically correct, excellently in all phases? How did they learn it? How did they figure it out? It just came natuarally to them, I guess. Perhaps, being educated at an early age in the classics is a huge advantage. It seems that, besides being genuises, the quality of their education had something to do with it.