How does the conflict that between the Western and Igbo culture leads to the downfall of Obi?

Obi never fully reconciles his twin identities as a member of the Ibo tribe and as a colonial civil servant. Torn between these conflicting identities, he ends up as neither one thing nor the other. Obi comes to resent what he sees as his tribe's primitive, barbaric customs. Yet at the same time he cannot completely break away from his past. For one thing, he wouldn't have been able to land such a plumb job in the civil service without his people's assistance. And once safely ensconced within the upper echelons of the Nigerian bureaucracy he's expected to return the favor through the awarding of government jobs to his clansmen.
Obi comes to realize that his Western education has not adequately prepared him for life in colonial Nigeria. He has fallen victim to one of the many paradoxes of Western colonialism. Western values are supposed to be modern and forward-thinking, supposed to liberate the indigenous people from superstition and barbarism. And yet in practice they institutionalize corruption, both moral and financial, meaning that even those like Obi who want to live their lives according to Western ideals are unable to do so.