Muhammad did not introduce monotheism into a world that had never heard of it. The hanifs had already tended in that direction through their focus on ‘the God’, Allah. Nor should we think that the Arabic world was suffering from materialism, and that Muhammad introduced to them a message about an invisible spiritual world that they had never considered real. On the contrary, his contemporaries lived in a highly spiritualized desert landscape. The distinction of Islam was to insist on monotheism over and against all other forms of devotion. So while Hinduism, for example, can be seen as a tapestry of deities all acceptable as objects of devotion while at the same time teaching that over and above all of them there is Brahma, Islam’s innovation was to wipe the slate clean of all lesser deities and demons so that Allah could be acknowledged as the One and given the praise due to Him as the Real.
Muslims consider this ‘pure monotheism’ to be their contribution not just to the Arabic context but to the religious world as a whole. Christianity for its part erred by deifying Christ and by arriving at a notion of the trinity that can be reconciled with monotheism only after some theological gymnastics; Hinduism, for its part, fails in the way described above. Thus Islam brought monotheist to Arabia and to the world, and this is its central message.