Why is Islamic State (ISIS) the first Islamist rebel group to claim to resurrect the caliphate? It seems like someone else would have tried this strategy some time in the past century, even with the risks associated.
1) Previous Islamist groups were (and arguably still are) products of national struggles and have a nationalist focus and nationalist objectives. The notion of a caliphate is transnational, eroding the very boundaries that movements like Hamas, Hezbollah, the FIS (Algeria), and even arguably the Taliban, sought to either liberate or preserve.
2) Previous Islamist groups were focused on driving out or defeating the crusader/ colonial infidels, not the Shia. The caliphate was associated with the earliest period of Islam, but it is also associated with the Shia, Sunni schism. This history is being reconstructed in the present as part of the struggle in Iraq and Syria. I cannot stress enough how modern this reconstruction of sectarian strife is for most of the region. The rifts were there but the frenzied jingoism around the “Shia” threat in predominantly Sunni countries is really new (I am still having a hard time getting my head around some of the stuff I hear). So there is a contemporary purpose for this reincarnation that didn’t have relevance to the struggles in Lebanon or Palestine.
3) Not many people want to live under the caliphate and smart groups know it. The extremism and brutality of da’ash is really off-putting to your average guy on the street. They don’t see this as legitimate resistance very far beyond the really radical fringe. Smart groups know that the national-religious combo allows for cross-cutting alliances; these guys leave no room for the aging, Christian Marxists who stand up and cheer (with whiskey in hand) when Nasrallah rails against the Zionist entity on satellite TV.