I am reading a book called The Best American Essays of the Century. One thing I keep noticing is a lot of the sentences in this book are very long — 5 to 6 lines. I read a lot of articles on the web, and the difference is obvious to me. In my opinion, contemporary writers keep their sentences short. Obviously there is not one way to write, but what I learned in college was to not make sentences too long and keep varying the length of sentences — not just too short in particular.
Now coming back to the question. What was the reason for this paradigm shift? I understand languages, including English, evolve over time. What was the main reason(s) behind the change?