Why Does The Author Includes This Portion Of Okonkwo's Exile In The Book?

I think the author included this part because the end of part one Okonkwo killed Ezeudu's sixteen year old son. So the author probably included this to show he was exiled for seven years, what would happen and how he and his village had to start over. He has to leave everything from his village, wives, his compound and his best friend Obierika. But Obierika helps the villager set his compund on fire. So when he starts over its ever harder than before. I know starting over is really hard especially since his village had all become weak and they didn't fight with their guns or machetes. And planting seeds isn't easy either because we don't control the weather so who knows when it is going to rain. Also in part 2 we meet the missionaries who in the story plays an important role, a white man who doesn't talk, and how Abame was wiped out after they decided to kill the white man.