It comes down to the importance of settlement services in place for newcomers. If they end up in a community where there are no services available to support them, they'll probably leave that community.
By the way, I attended a meeting with new immigrants to Canada. They told me that immigration is a personal life project for them and that when they leave their country, they do it to start a new life. They therefore choose a place where they can be sure they can live that new life.
Immigration is therefore a very personal choice. Immigrants don't choose based on the percentage of francophones in a region, whether it's 5% or 32%. For them, it's a personal life project.