Agatha Christie is part of an interesting theory. Apparently, she was not a great writer initially. And then she disappeared when she divorced her first husband. And when she reappeared 11 days later, she was a great writer. I have read analysis of her first novel compared to her later ones and they say that they weren't written by the same person.
Robert Lewis Stevenson is another author with a similar story. He disappeared a poor writer and reappeared as a genius.