The picture that Achebe paints is not a very positive one, using the story to depict a colonial power that enters and then brings about the death of the Igbo culture. Through the Christian religion as well as technological advances, the agents of colonial power enter the village and work tirelessly to convince the Igbo that their ways are the ways of the past and of ignorance and that the ways of the white man are better. They create rifts in the village and seek to exacerbate those by continuing to point out ways that the village is backwards.
Eventually the interference of the white men and the conflict of their ways with the traditions of the Igbo bring about the death of the Igbo culture signified in part by Okonkwo's suicide.
It is colonialism that destroys the traditional setting of the Igbo and causes all sorts of undermining. Colonialism is depicted as an artificial source that enters and subverts the traditions and bonds that had existed for some time. Through Okonkwo's eyes, colonialism has wrecked the village, transformed the characteristics of people there, and changed his own family's dynamics between he and his son. Achebe's depiction is one where outsiders entered and were able to undercut all hopes of collectivity with the lure of material riches and impositions of outside power. In the end, the destruction of Igbo values might have been inevitable, but Achebe paints colonialism as the prime culprit that hastened the process.
Social stratification was removed by colonialism, the order of the Igbo culture was destroyed! thinking by not thinking about it, Africa came to depend on colonialism, in a way that Africans relied on the European's riches and power.