A case can be argued for a "yes" or a "no" answer for this question, I believe.
The choices Okonkwo makes are largely responsible for his downfall. He is determined not to be like his father, who was considered weak, so this is a huge motivating factor in everything he does. He mistreats his children and his wives, and he kills Ikemefuna even though he has been warned by the tribal elders not to have anything to do with this killing. He does not want to appear weak, so he kills a boy he has come to love like a son. He beats his wife and accidentally shoots the son of a tribal elder, so he is banished for 7 years. While he is banished, he continues to make poor choices, and when he returns to his native village after his banishment, he is the cause for his son converting to Christianity and finally, he decapitates a court messenger and commits suicide. All of these are bad choices. The final choice of commiting suicide makes him unclean and alienates him from his tribe forever because suicide angers the earth goddess.
For the opposite point of view, one could argue that the forces against Okonkwo are overwhelming and they are the cause for his life "falling apart." Okonkwo fails to adapt to change, stubbornly adhering to old ways that do not seem to work anymore and because of this, he is in constant conflict with people, his family, his gods, the colonizers.
What do you think?
Naturally, the previous thoughts were accurate. For me, I place focus on how Okonkwo perceives life when he returns to the village. I would say that when Okonkwo comes back to the village to find life has changed, the conditions that caused this change has to have some level of responsibility for causing him to react and interpret the world the way he does. Certainly, his downfall is due in part to the changing world and values of the Ibo and the presence of Colonial society interfering in the traditional setting in which Okonkwo asserted belief. We can blame Okonkwo for not being able to fully able to react properly or understand the nature of the change around him. Yet, one has to feel a certain amount of empathy for him in not be able to process the imposition of Christianity, the presence of Western values that undermined the traditional Ibo ways, as well as the idea that the bonds of collectivity and solidarity that once used to rule the village have been supplanted with individualism and materialism. Certainly, he should have understood these forces in a more constructive manner. Yet, upon his return to the village, the stunning level of change was one that impacted him greatly and for this, I am not certain that I am able to assign to him all the blame for his downfall.