Here is a key passage:

Poor people in Kenya are average people who happen to live in an extremely poor country. Basic habits of hard work, diligence, and thrift don’t necessarily pay off in an environment where everybody is so poor that hardly anyone can hire you or pay for anything you make. Dumping cash on people in these circumstances really lets them level-up. By contrast, the domestic poor are — unless they are recently arrived immigrants — often people who, for one reason or another, are struggling to get their lives together in a very wealthy country. If they were thrifty and diligent, they wouldn’t be poor in the first place. Putting money in their pockets doesn’t make them thrifty and diligent, so it doesn’t really alter their lives that much.