
Max M. answered 02/13/20
Harvard Literature major with 20 years of coaching writers
You may have long since lost interest in this question, but just in case you or anyone is still looking and interested, I'll throw another thought in there.
The word both answers are kind of circling around is fashion. Long novels were in fashion. Economic incentive is definitely a huge factor, and printing tech made it possible, and it's true not just in England (pick your top five English novelists and your top five Russian novelists, and put all their books into one pile each--which pile would you guess weighs more? Tough call...), but lit is just as driven by unpredictable fashion as clothing. And when one style gets popular, approximately the same percentage of the work will be great as in any other style.
But if you're asking about why they wrote so *many* things as well as so many *long* things, can I ask who or what you're comparing them to?
Dickens wrote 15 novels plus a bunch of stories, novellas, and articles; Balzac wrote 36+ novels, plus about the same number in total of novellas, short stories, and plays
Thomas Hardy wrote 16 novels, a bunch of short stories, and of course a ton of poetry; Isabel Allende wrote 20 novels plus nonfiction
The Bronte sisters between the three of them wrote about 9 novels and a volume's worth of poetry; Haruki Murakami has 14 novels and counting, plus short stories and several volumes of nonfiction
and so on...
Sure I'm stacking the deck with those examples, but what exactly is it that's making you think of the English as that much more prolific than any other culture's great authors?