Why do you assume that nobody in the Pakistani military may be motivated by factors such as religious extremism, above and beyond simple utility calculations?
It may very well be that some people in ISI were sheltering Bin Laden for no reason other than that he was a genuine hero to them.
It's very possible that some people sheltered him outside of the official policy or whatever. It's even possible that it was ISI / Pak gov't official policy, but again there's no proof of any of these things.
It is also possible, that he just was able to hide from the entire world close to an army base in a compound he never exited from, never approached a window near, and never accessed internet from.
Everything is possible, there's no proof either way. And I don't see what the govt or army or ISI would gain from harboring him as a policy matter. If someone is crazy and personally helped out, that's not what most people are even implying is it? That's much more reasonable and doesn't really have much to do with the current conflict and the claim that the latest terror attack was sponsored by Pakistan (again, possible but not proven)
It may very well be that some people in ISI were sheltering Bin Laden for no reason other than that he was a genuine hero to them.