It absolutely evolved over time.
One scholarly position is that the identification of Yahweh with Ēl is
late, that Yahweh was earlier thought of as only one of many gods, and
not normally identified with Ēl. Another is that in much of the Hebrew
Bible the name El is an alternative name for Yahweh, but in the
Elohist and Priestly traditions it is considered an earlier name than
Yahweh." - From here
There is more to the belief El & Yahweh were separate at one time if you dig into it.
And
"The biblical narrative is also sorely challenged by the findings at
the site of Kuntillet Ajrud, in the Sinai desert, where archaeologists
discovered inscriptions on rock dedicated to “Yahweh of Samaria” and
“Yahweh of Teman” – showing that this god was worshipped in multiple
incarnations at different sanctuaries. Dated to the early 8th century
B.C.E. (just a few decades after the Mesha stele), these inscriptions
at Kuntillet Ajrud also include a crude engraved drawing of a male
deity and a female deity, and describe the latter as Yahweh’s
“Asherah.” " - from here
The cult of Yahweh began as henotheistic, and there are many examples of the infringement of other worship practices, like Moses & the golden calf incident, and not mixing animal & plant fibres in a law called shatnez linked to practicing Canaanite rituals - dietary laws like not cooking a calf in milk have also been linked to proscribing rituals. These weren't being dismissed as superstition, but as empowering the deities of other peoples, & being unfaithful to Yahweh. Several Biblical stories allude to the belief that the Canaanite gods all existed and were thought to possess the most power in the lands of the people who worshiped them and their sacred objects; their power was believed to be real and could be invoked by the people who patronised them. There are indications Lilith was a protective deity of newborn children, who's amulets were used controversially into monotheistic times.
In Judaism the relationship with the deity progressed through a series of fiats, Adam & Eve's, Noahide, Abrahamic, Mosaic, and various others. So, 'no gods before me' became a specific crime against god with the commandments given to Moses.
But before that, Abraham is a really interesting example of embodying the beginning of what has been called The Axial Age, the time when from the 8th-3rd centuries BCE cultures across the world transitioned from sacrifice-led rituals to more legalistic traditions. Abraham was willing to sacrifice his first born. Like he was becoming aware even the greatest sacrifice he could think of, wasn't enough to show his obedience to god. Sacrifice was still practiced until the last fall of the Temple, but I would describe this experience of Abraham as 'reaching beyond sacrifice' for something more, as why he is the patriarch of 3 major religions.
What are called angelic beings in Judaism like the ophanim which appeared to Daniel, would have been called lesser gods in other traditions. Placing allegiance firmly to one deity above all had a primarily political impact, as discussed here: Why is the emergence of Monotheism a cultural milestone in the development of mankind?
There is a pattern that religious variety & tolerance can thrive in highly military unified states like Ancient China & Rome, but political dissent not, whereas religious conformity is extra valuable where military unity is not, like the Holy Roman Empire able to mount Crusades, but also to encompass many cultures languages & political systems, or Ancient India where travel was always tricky. It can also be seen how the Islamic Ummayyad's were able to go from being a desert tribe confederation to ruling 29% of the world's population in less than a century of becoming monotheistic.
So set in this context, was Jewish monotheism unique?
The Egyptian pharoah Akhenaten attempted to introduce monotheism. It didn't go well, & it ended after his reign.
The transcendental monist take on Hinduism interprets all beings as 'faces of Brahma', which I would link to what Plato was innovating with his forms, a framework to find political unity across religious divides.
Judaism was innovating, being the first to explicitly declare itself monotheistic, but as mentioned many continued to partake in other rituals. What religions say about themselves is rarely as important as what they do. I would look to Durkheim's understanding of what religion does & how it works, that it's about the social binding power of enacting shared attitudes to what is held sacred & put beyond question. Judaism was reducing the scope for 'religious entrepreneurialism', & consolidating the laws & principles into one structure, in a legalistic way in the sense of based on precedent. You see the same pattern later in Sikhism. I'd say this process of enforcing religious unity, allowed greater freedom to disagree in other matters, & Jewish culture famously celebrates being argumentative). Simply declaring only one god is important isn't the big deal, it's this transition from sacrifice-based religion, & building a centralised unified orthodoxy that holds space to disagree elsewhere (religious unity patching up political disunity). And that, I think, is the bit that matters Judaism did first.
Plus all classes taking the same day strictly off work, that was an underappreciated innovation with deep repercussions (Babylonians had similar numbers of rest days, but far less strict or universal).
