A microwave is not a substitute for a stove. Have you had microwave meats? Tried to brown vegetables in the microwave? These two things alone mean that you have the initial problem of changing people's food. In addition, most folks would need to buy new utensils and cooking vessels for that microwave and hope there is a bakery nearby that they could afford to buy bread from.
There is also an education cost that is much, much greater than moving from a fire/charcoal to the stove. Your cooking methods are very similar when moving to the stove and most of the education lies in operating your new device. Traditional cooking doesn't transfer well to the microwave, so someone is going to have to teach folks.
I much prefer a more traditional stove setup with a solar installation, even if it is a hot plate or something similar. But I realize that having a pellet stove is going to spread more quickly simply because of costs, portability, ease of distribution, and lack of failure due to weather.
For a lot of poor Africans this isn't a problem.