He specifically explained that in the video. He liked how in the beginning when he started to write he could create new things and work on what he was most exc

He specifically explained that in the video. He liked how in the beginning when he started to write he could create new things and work on what he was most excited about, but as he wrote books he started getting shoehorned into writing the sequels to the books, limiting him in what he could do and what he wanted to write. When some unexpected, free writing time opened up - he used it to go back to that and enjoy himself writing books that didn't have any preexisting limitations.