Those who claimed that they have established caliphate have consulted Ahl al-hal wa-al-Aqd (Scholars qualified to elect or depose a caliph on behalf of Muslims) and all Muslims.
The fact of the matter is that they did not consult anyone but a few people from among the adherents of their group who in no way represent the view of all Muslims around the world. Moreover, if we accept their claim, for the sake of argument, we will find that this only applies to some limited areas in Iraq and Syria. There are, however, many Islamist factions and groups working in Iraq and Syria who accuse each other of disbelief and fight each other.
Furthermore, the oath of allegiance was taken from many people under compulsion and coercion. They were afraid from being killed or deprived of their maintenance. Consequently, their oaths of allegiance are null and void. In fact, this is the case of most people living in the lands seized by these terrorist groups.
Those terrorist people do not know Islam of which they speak and take as an instrument for achieving worldly gains, but Allah exposed them and exposed their ignorance and lies as Allah refuses except to perfect His light.