The Quran itself also confirms that the pre-Islamic Arabs believed in Allah:
If you asked them, “Who created the heavens and earth and subjected the sun and the moon?” they would surely say, ” Allah .” Then how are they deluded?Quran 29:61
It is well known that Muhammad’s father’s name was Abdullah. Servant of Allah.
From the article:
In the religion of the Meccans and the other pagan tribes of the Hijaz, al-Lāt was not the wife of the high god Allāh but was one of his daughters, along with the other two chief goddesses, Manāt and al-‘Uzzā The gods and goddesses of the pre-Islamic Arabs were usually tribal deities; legendary ancestors; spirits of place (jinn), or personifications of natural and social phenomena unique to the individual Arabian tribes: although there were certain deities that were widely recognized throughout the pre-Islamic Arabian peninsula. The religious beliefs of the Arabs often differed from region to region; smaller tribal pantheons being found among the merchants and Bedouin of the Hijaz and Najd; with more advanced religious structures thriving in the Yemen. In the sparse desert regions inhabited by nomadic Bedouin such as the Nefud desert, religious thought took the form of a practical animism chiefly concerned with pastoralism and tribal life – this is not to say that the pagan Bedouin did not enjoy a rich spiritual experience: their belief in many gods, angels, spirits, ancestors and sacred sites confirms otherwise.Arab Paganism
This idea of going from many gods to one god actually has repeated itself in history several times. See the following video which is a summary of Karen Armstrong’s “A History of God” and documents this process:
This is the same process Muhammad performed on Pre-Islamic Arabia. He eliminated all of the lesser gods and left only the main high god.
Read more about Arab Paganism here