A typo. Should have been: "What fuels the `creep of Islam?'"
Good question...one I think that goes to the heart of the matter. And there are several points of view one might consider.
First, from a practical point of view, since Islam is designed to clash with other religions, it will either shrink into non-assimilation and standoffishness or it will spread with the idea of having others assimilate into it (conversion, by choice or force)...both are not only functional parts of Islam but are dictated by the Quran. Also, the Quran clearly states that ultimately Islam must be the only religion in the world...and that leads to the establishment of the World Caliphate. That is the goal of all "real" (read "devout") muslims.
Secondly, islam creeps into a society by the call to true Islam by devout Muslims and imams ("Dawa" is the call to non-muslims, but it is also a call to lax and apostate muslims). Islam, at its heart, is not moderate (not the Islam of the Quran and of Mohammed). This call by real muslims to "moderate" or "apostate" muslims is particularly compelling since it is a call to come back to the god of your family and your fathers.
Thirdly, one has to ask if Islam is a real religion, i.e. is Allah a spiritual force...does he exist? If one imagines that Allah is the spiritual force that spoke to Mohammed and guided Mohammed, one can conclude by reviewing the life of Mohammed that Allah, if he exists, is not a benign force. Mohammed's life was filled with violence, piracy, rape, and greed. Not exactly holy to say the least. At any rate, if their is a spiritual force named Allah, one might conclude that such force has a motive in the spread of Islam and works within Islam and in the minds of the serious believers of Islam to spread this religion. I will leave the determination of potential motives to you...but you see where such a thing seems to be heading.
It illustrates (much better than I can) the actions of the "creeps" of Islam.