Maybe since they have been thrown into disarray by the Afghanistan campaign, they are like a cornered animal, lashing out at anything and everything, friend or foe. Trying to stay relevant, and on the front pages (like a certain ex-President).
Because Islam cannot stand contradiction: You must convert or die. Europeans are nothing if not atheist.
Here's the sick part. Al Qaeda wants Europe pissed off at muslems. So far they have not succeeded in creating a world wide holy war because most muslems are still waiting to see what happens next. They want all of the west pissed at muslems so that the muslems will feel that they have no choice but to rise up to defend Islam.
So far Al Qaeda has been isolated, which is a very good thing for the west, a bad thing for Al Qaeda.