You are all over the place.
Individuals do all kinds of stupid things. What use is in believing what they say?.
That's hardly denial. It's just very uninteresting, to me, to figure what's in the mind of any specific terrorist. They may believe whatevs, and indeed many probably believe in the advent of a Islamic caliphate. But they're just tools in the hands of people playing geopolitics from the security of their homes.
I'm making the case that rejecting a nationalist narrative (often just for the sake of sticking it up to the Muslims) is missing a great part of the story.