Docu-Reality: The Re-Packaging of Reality TV as Docu-series

Keeping Up With The Kardashians is reality TV. I Am Cait is a docu-series. What's the difference, and what's the reason for the change? Across the board, documentary series have exploded (Making a Murderer, Chef's Table, OJ: Made in America, The Jinx). Is reality TV trying to repackage their reality TV content to catch the wave?