Why dos chebe spend so much of the first part of the chapter describing Unoka?

He spends so much time describing Unoka in order to help us understand the character of Okonkwo. All of Okonkwo's actions and desires are based on the way he feels about his father. His father was unsuccessful, therefore he has no patience for men who aren't successful. Okonkwo on the other hand, is determined to be a success.