I'm curious. How accurate are the foundational legends of the Swahili city states claiming to have been started by Arab and Persian nobility? I can't help but shake the feeling like this was perhaps in part legitimization by connecting the ruling families however distantly to Mohammed.
There is always more to say, but I covered what's known as the "Shirazi origin" thesis here in some detail a couple of years ago in a monster post on the government of Barawa. You might like to review that response (under the section "A little history of Barawa") while you wait for fresh answers to your query.