Mecca itself seems to have been essentially devoid of monotheists except for a few exceptions such as Muhammad's cousin Waraqah ibn Nawfal, who was some sort of heretical Christian. This said though, the entire peninsula filled with Jewish influences in the centuries prior to formation of Islam. We know that in the centuries prior to Muhammad, that there was a Jewish kingdom in modern Yemen, and that probably allowed for a great deal of ideas to swirl around in the Hejaz for a few centuries, even while they were still pagans. At least in one case 20,000 Christians were burned to death in a ditch under the Jewish king Dhū Nuwās. The Qur'an has been found to have material from the midrash and Mishnah within it as well, which shows that there was indeed some sort of non-Christian Jewish material being incorporated into early Islam. As I said in my previous post, it was for centuries prior to Islam that the Arabs began to wake up to being Ishmaelites. You'd be surprised how many references there are in the literature. For example, Sozomen writes in his Ecclesiastical History, finished around ~450 A.D.:
>Some of their tribe afterwards happening to come in contact with the Jews, gathered from them the facts of their true origin [their descent from Abraham], returned to their kinsmen, and inclined to the Hebrew customs and laws. From that time on, until now, many of them regulate their lives according to the Jewish precepts
https://www.newadvent.org/fathers/26026.htm
From Irfan Shahid's "Byzantium and the Arabs in the Fifth Century", referring to an account of Theodoret of Cyrrhus (died 5th century A.D.):
>The second reference comes in the Life of Simeon Priscus, the famous solitary who established himself on Mount Amanus, whence he moved to Mount Sinai. Before living on Mount Amanus he had lived in a cave, and his miracles had attracted many of the neighboring barbarians. These are described by Theodoret as Ishmaelites: "those who proudly derive their descent from their ancestor Ishmael live in that desert"
https://libgen.is/book/index.php?md5=D218041A306164DFDB6CA2F82CC15A6C
Now, most interestingly, Sebeos says the following in the 7th century, speaking about the Muslims and Ishmaelites in particular. The Arabs are 'enlightened' by Jews fleeing from Edessa, and the Jews enlist the Arabs to assist them:
>Twelve peoples [representing] all the tribes of the Jews assembled at the city of Edessa. When they saw that the Iranian troops had departed and left the city in peace, they [122] closed the gates and fortified themselves. They refused entry to troops of the Roman lordship. Thus Heraclius, emperor of the Byzantines, gave the order to besiege it. When [the Jews] realized that they could not militarily resist him, they promised to make peace. Opening the city gates, they went before him, and [Heraclius] ordered that they should go and stay in their own place. So they departed, taking the road through the desert to Tachkastan to the sons of Ishmael. [The Jews] called [the Arabs] to their aid and familiarized them with the relationship they had through the books of the [Old] Testament. Although [the Arabs] were convinced of their close relationship, they were unable to get a consensus from their multitude, for they were divided from each other by religion. In that period a certain one of them, a man of the sons of Ishmael named Muhammad, a merchant, became prominent. A sermon about the Way of Truth, supposedly at God's command, was revealed to them, and [Muhammad] taught them to recognize the God of Abraham, especially since he was informed and knowledgeable about Mosaic history
http://www.attalus.org/armenian/seb9.htm#30
The next chapter by Sebeos mentions that the Jews only had the aid of the Ishmaelites (Hagarenes) for a short time, and wished to use them to rebuild their Temple:
>Now I shall speak about the plot of the Jewish rebels, who, finding support from the Hagarenes for a short time, planned to [re]build the temple of Solomon. Locating the place called the holy of holies, they constructed [the temple] with a pedestal, to serve as their place of prayer. But the Ishmaelites envied [the Jews], expelled them from the place, and named the same building their own place of prayer
http://www.attalus.org/armenian/seb9.htm#31
It's not entirely impossible that the rabbis used the Ishmaelite descent of the Arabs to use them as shock-troops against Christendom, and once Muhammad was demonically inspired by Jibreel, the rest was history. I have recently heard that the first reports of the Jews concerning Muhammad and Islam were positive, but I will have to investigate more.