They were radicalised because they were low-life thugs, marginalised by society and bad politics.
http://www.bbc.com/news/magazine-35890960
They were not radicalised because Brussels is full of Muslims. A large Muslim population and terrorists are not mutually exclusive.
Unfortunately, most of the people in this thread are anti-Islamic xenophobes and this is a waste of time.
yet we don't see African Americans in Detroit and Baltimore blowing themselves up....
oh its Western foreign policy
oh its because they're marginalised
********, it's because they follow a messed up ideology - those other factors can act as catalysts, sure, but they're not the root cause. The root cause is fundamentalist Islam and trying to blame other factors is just sticking your head in the sand.