Ok, Publius, since you are so knowledgeable about the area, why are there so many Eritreans here in Seattle? I always found it interesting that they chose to settle here, of all places.
As to why people picked a place so different from their homeland, I'm not sure. I suspect it was the booming economy, once we recovered from the prolonged recession of the early Nineties.
I put myself in the position of a Russian immigrant, used to snow and icy cold, settling in a place where winter is tolerable without vodka. Likewise, I imagined people from Africa, used to dust and drought, coming to a place where the summer is a joy to behold, and it rarely gets over 80 degrees.
I doubt it had anything to do with cultural similarities.