That's the point, they are sporadic. Islamic terror attacks on the other hand are not, they are frequent and to be expected and this is when it becomes apparent that there is an issue.
Firstly; it is cyclical, there have been increases in terrorist attacks during periods of history before. Nobody is claiming this is not an issue.
Furthermore; extremism is on the rise, not just in the Middle East. When 'the West' bombs your country in to the ground, it can be quite easy to gather groups of disenfranchised people to fight against a cause, under false pretence.
Interesting that we (British Government) is happy to sell huge amounts of weapons to the Middle East, and strike deals with countries that directly fund terrorist.