My 2 cents
I think it is likely that these attacks were put together quite quickly in the aftermath of the capture of the suppose mastermind of the Paris attacks earlier this week. Especially since he was captured alive, and claimed he had recruited a new network, it stands that the remaining members of the cell would either go to ground, or execute their plan before the authorities closed in on them. Unfortunately for the people in Belgium, the extremist chose to attack today.
__________________
|