As an academic researcher, I believe that at an unspecified time, some unknown people, may have possibly engaged in potential activities (possibly in response to grant money!) while seeking to justify their existence to other academic researchers.
Besides, there just seems to be something wrong with the logic of associating developing a larger brain on a high protein diet made up of three of the most dangerous animals one can think of to hunt (humans, hippos, and crocs). Good luck living off those and surviving long enough to breed!.
All other species with very large brains are aquatic mammals such as dolphins and whales. Given humans' lack of fur, subcutaneous fat layer, and partly webbed fingers and toes (none of which are possessed our primate "relatives") I would think that would be a more worthwhile angle to make up useless theories about.