Gandalf
Horn Tooter
Actually, there are many sets of writings called "the Bible." and it brings forth several perspectives on God and gods. Then, at some later point, it takes all these Sumerian and Babylonian ideas of deity and gloms them all together into "God." YHVH is a different God than El. Who is a different God from ... God. So, the concept of "true God" is a rather ineffable concept in the Bible.
More so in the Qur'an, when we say monotheism in terms of the word tawhid it is a big overstatement because with the constant addition of intercession and emphasis on uniqueness it leaves to raise not just dubious claims but very implicit ones. The Qur'an makes the argument there can't be 2 gods that rival each other because creation originates from one source and that a single unique source can't give birth to another unique sources or else neither is unique.
Followed by the fact that no Muslim can prostrate to no man yet Iblis must prostrate to the first of men, Adam and then later added that only the greatest of people "could" be prostrated toward by parable of the power of patriarchy.
You can understand why ghulut sects existed amongst the Shia from the 1st century and removing the concept of hulul (incarnation of divine) and defining monotheism became a big problem.
I just think people misunderstood the power of Emanationism and the fact the Qur'am confirms Gnostic thought so much many heretical groups add it back in but close the religion off by making it an ethnoreligion like the Druze and Nusayi.
In short why believe in the incarnation of Isa when you can make that applicable to every prophet and determine a hierarchy.