Some Muslims wanted us to fear Islam. I guess that worked.
It could be nuclear fallout from Japan, or Islam, or H1N1, or drug cartels in Mexico, or Canadian healthcare, or communists, or the Arab Spring, or any number of other things that for all intents are purposes are almost entirely non-threatening to the average citizen on the street.
The focus of the fear is completely irrelevant. The primary goal is perpetual fear itself.