In short, because the Western democracies have never been weaker.Ask yourself this: why are there Muslims ready for full scale war, now and not before?
They have no religion worth mentioning, their cultures are all 'multi' (which denies and negates their own cultures) the work ethic is disappearing and they have no real heroes, nothing to inspire them the way Islamic leaders inspire other Muslims. The family has become institutionalized with those once called 'adults', those who were once responsible for their family and community, becoming an endangered species.
Islam is the strong horse and the democracies the weak horse, just as Osama predicted. We are ripe for it.