Okonkwo's downfall progressed throughout the story as he went from a man of high stature and respect to an exiled outcast in his clan. His personality traits and the arrival of the white man were both contributions to Okonkwo's downfall of which he loses his position in his clan and commits kill their self
Because the union had pushed them out of their land and hurt them so much, they wanted to seek revenge on the union. They had also hoped that the confederates wouldn't push them out any more.