Because muslim populations are a minority, and islamism only attracts a fraction of that minority. Minorities usually don't have a political party. But the recent terrorist attacks and the large number of european fighters in ISIS makes the rise of Islamism in the West only too obvious. And keeping in mind that violent partisans are usually a fraction of the sympathisers, like violent marxists activists in the 70s were only a fraction of communists sympathisers.

Islamism as you call it is two different but similar flavors of political Islam; Wahhabism (think Saudi Arabia) and Qutbism (Muslim Brotherhood). Neither are brand new to the region, but both are around 100 years old.

While the philosophies are around 100 years old, this doesn't mean the Middle East has embraced those philosophies for the last 100 years or that it does today.

There has been a measurable trend to right-wing conservatism and religious affiliation in the Middle East which can be seen not only in Saudi Arabia and Egypt, but also in Israeli society, and in Lebanon. This shift has happened over the last twenty years or so.