Their existence was a threat to jomo's selfish interests, he deliberately ensured thet they didn't become landowners and remain financially powerless. While he grabbed all the land he could.
The story of .ke independence struggle and aftermath as taught in schools and especially the 844 system, is a pack of revisionist lies.
E.g if you ask any 844, who was the leader of Mau Mau ?
99% will tell you it was Jomo.
The kind of lies that people in some countries riot, do book burning and demand for the true story to be told in school text books.