Not living Oulu but living Finland. Oulu is pretty remote even in Finland's standards so people don't move out so easily. That created a situation where startups had suddenly lots of highly skilled engineers to hire cheaply and that created a boom in the town.
There are various reasons in my opinion. People, who were laid off from Nokia, were highly educated and many of them were well-respected in their fields so it is quite easy to lure some new companies to Oulu (Mediatek, Nordic Semiconductor etc.) In addition, people were also used to make business internationally so it was lot easier to start new companies with that kind of experience.