1. Trying to make their ideology more dominant (aka spreading Islam in general)

I find this the least likely as the main goal. Also, if this was the case, they are counterproductive. So far Islam was very successful in the last few decades to gain a bigger and bigger foothold in the Western world, helped both by demographics and by the predominantly left-leaning political elite in Europe encouraging the acceptance of and submission to Islamic culture in Europe instead of encouraging the immigrants to abandon their culture for the culture of the host nations. However, the recent terrorist attacks, and the many atrocities committed by the recently arrived asylum seekers, while hurting European economy, will probably lead to Europe being more skeptical regarding Islam, which might reduce the chances of Islam peacefully and silently spreading. So these events, if indeed orchestrated by ISIS, might have been successful in harming the economy of their enemies, but I don't know what an effect they had on the spreading of Islam. I'm tending on believing in a negative effect, but I just don't know enough factors to know it for sure. I believe the violent attacks in the Western world are done mostly to show their own followers at home how powerful they are and how weak their enemies are.

In fact, these results make it hard on the Islamic people who wouldn't join ISIS. This makes ISIS more attractive to these people. If a government oppresses a group than every anti-government group seems less oppressive to that group, both because oppression is relative and because of in-group vs. out-group dynamics.