This might be of some interest.
When I hunted with Mark Sullivan, he told me he hunted lion near Tsavo on the Tanzanian side of the border. He maintains that lions of Tsavo have manes like male lions everywhere, and that had the lions been maneless, they were simply immature lions, rather than being an unusual subspecies.
This theory raises many possibilities, one of which is that lion's mother may have died before being able to teach the cubs to hunt natural game, and humans were easy. Another possibility was that the railroad workers were consuming all the plains game in the area, leaving nothing for the lions but them.