3. The elected regimes can use the educational system, religious institutions and media to indoctrinate the public and ensure continued support. They can use jobs and the economy to control patronage and votes; create or control trade unions and professional associations.
By controlling the religious institutions, Islamists can get rid of traditionalist Islam and entrench their own interpretations.
And let’s not forget the greatest prize of all: control over the military, a plan that might include creating separate elite units (Islamic Revolutionary Guard Corps in Iran, Revolutionary Guards in Iraq, Republican Guards in Syria, etc.)
4. The intrinsically radical nature of the Islamists themselves: if you’re taking your orders directly from the Supreme Being and in accord with the most sacred religion, you’re unlikely to change your views. Western materialist cynicism goes too far in thinking Islamists will sell out for luxury and power. Besides, they can enjoy luxury and power (see Iran) without having to throw away their principles.
Moreover, we are not dealing with Communism in the era of Leonid Brezhnev here. The Islamists are a relatively young movement, unbowed by failure and not jaded by long possession of power. They genuinely believe the future belongs to them. Maybe they will become tired and lose their confidence in 30 or 40 years, but not now.