Knowing how Belgium handles their minorities in Brussels, it's not a big surprise.
The fact that this happens now is neither a surprise. Salah Abdeslam has been caught, and there were messages that he wanted to cooperate with the Belgium police. Whether it's true or not, if they were planning something, and he knew about it, waiting was not a real option.
Could you elaborate? Is this a banlieu situation?
Belgium has big problems between the Flemish and French speaking parts, and particularly in Brussels it's politically very complicated. For some city wide measures, they need like 26 police commanders to agree. I don't know the numbers, but it's very complex to get all people in line. And I'm not talking about the people in the street, this is about city councils, police departments etc.
Brussels itself resembles the EU in this respect.
This article discusses the mess that is Belgian governmental organization: http://www.politico.eu/article/belgium-failed-state-security...