I think the guy may have bought the land alright but took advantage of those who may not have known its true value or intimidated them to sell it. According to the old people (the before @Guka era), this mzee was a formidable force. He however did not get to shove people around too much in Central-they would of course not give up land easily. So he chose to take/buy/steal land elsewhere.

As to whether he stole, bought or just took.. i don't know if we can ever know. There has been enough time to right any wrong that may have been done....