The simpler explanation is that he both got paid more, and delighted in it such that even when he was quite successful and was getting paid quite well for appearances, he continued to write in his signature verbose and indulgent style.
An *even simpler* explanation is that "verbose" is subjective. What seems overly verbose and tiring when you are reading for two hours straight may seem just if you are reading one serialized section a day.
Shakespeare's plays were written to be performed, not read. Dickens was written to be read in small installments, not in long segments.