Why most successful Luo men marry Kikuyu and Kamba women

Why is it that most successful Luo men are either married to Kikuyu or Kamba women? Before you start crying like an ambulance in the comments, listen first.

Take Millionaire Polo Pespoke and his wife Mueni, for example. Ten years ago he was a hawker, water vendor, and sugarcane seller in Eastlands; and the lady stuck by him because she saw potential and applied patience....