You can see exactly the same with other authors. Asimov and J. K. Rowling, to pick two obvious candidates.
Compare "Foundation" with "Foundation and Earth" or "Foundation's Edge". Or "The Philosopher's Stone" with "The Order of the Phoenix". The former were well-edited and succinct. The latter were overly long, in some cases sorely repetitive with large amounts of padding, and a good editor could have cut them down by at least half without losing much.
Compare "Foundation" with "Foundation and Earth" or "Foundation's Edge". Or "The Philosopher's Stone" with "The Order of the Phoenix". The former were well-edited and succinct. The latter were overly long, in some cases sorely repetitive with large amounts of padding, and a good editor could have cut them down by at least half without losing much.
And let's not even get into Robert Jordan...
Even the best authors need an editor.