Just visit KACC website and go through their monthly, Q or annual reports you will see how boring the reports are, No single case involves the big fish.
They have hundreds of cases involving junior officers,how difficult can it be to use the junior officers to arrest the big fish since Its obvious the big fish always uses the small fish to do their dirty work.
By using these small fish they can make them prosecution witnesses and Nab their bosses.
'......to the acknowledgment of the mystery of God, and of the Father, and of Christ; 3 In whom are hid all the treasures of wisdom and knowledge.' Colossians 2:2-3