I think it is more than just trying to look tough, I think that he wants a united caliphate that he probably believes would be an equal to the United States.
Yes, well the caliphate UN is most corrupt, has no teeth, which is good, for it has no backbone. Even more, it has no principle, no rule of law, no consistency - just applied cronyism. Kofi Annan assured his son millions in commissions for the Oil for Food program. Wars are fought to protect those mercantilistic advantages. This is Mafia - and you are right, that’s what he wants.