I would argue that this great Southern African novel explores the good that power can accomplish by showing, in an almost exaggerated way, how poor leadership can stymie progress.
The powerful figure in this novel is Chief Matenge, who is desperate to hold onto the status quo (and his power) by any means required. To this end, he ensures that the co-operative project is delayed as much as possible. He ensures that numerous obstacles are placed in the co-operative's organizers' way to slow down progress.
In comparison, let us discuss the conversations that take place between Gilbert and Makhaya and all that these two are able to achieve in the community. Both men are enthusiastic about empowering others, which is another characteristic which leaders should display when they are interested in using their power to accomplish good things.
In a nutshell, it is the juxtaposition between the abuse of power showcased by Chief Matenge and the positivity embodied by Gilbert and Makhaya that shows the myriad good effects that power can accomplish for a community. This is dependent, however, on the motives of those in power. If, like Chief Matenge, a leader is motivated by greed and personal gain, then the power that he holds will be of no benefit to anybody else.