We can’t answer this question without a cautious examination of just what ‘monotheism’ means. It doesn’t mean that you believe that your god is the best god. That’s called monolatry. It doesn’t mean that you believe that only your god deserves worship. That’s called henotheism.
No, monotheism means something very specific. It means that you think that while you are worshiping a deity, everybody else is worshiping sticks and rocks. Instead of a world filled with magic, mystery, and wondrous cultures, the world is filled with people who never even had the chance to experience real religion at all.
Any other position is reducible to monolatry or henotheism. It’s a weird position with weird consequences that, even though it has an academic sounding name, can reasonably be attributed to one people, the Hebrews.
Monotheism didn’t develop in Hebrew culture overnight. It is recorded in the Hebrew Bible that even after Yahweh revealed Himself to be the one true God, many Hebrews still decided to worship other gods. It took centuries of wars and conquests for the followers of Yahweh to triumph. And then for thousands of years the culture and society of that part of the world, the Hebrews, who now called themselves Israelites, was theocratic, dominated by the one god they no longer had reason to call by any name other than God.
Monotheism simplified things for the Israelites. They built a culture, what we today call a covenant, that allowed them to live in harmony with what their god wanted. It didn’t simplify everything, for instance if and when they had to live under foreign rule, with their conquerors expecting obeisance to their gods, the Israelites had to compromise.
But they slowly worked on these ideas until two things forced them to a reckoning. Hellenistic culture kept encroaching on their way of life. And the Romans eventually turned the region into vassal states with appointed governors and, more importantly, religious leadership.
But a few short decades before this reckoning happened, a particular prophet offered the Jews a new way to live with and approach the deity, a new covenant. This prophet’s words are still heeded today, and the religion that prophet started survived and thrived, succeeding even the empire that razed their temple to the ground.
It could be said that the Israelites were the first society to collectively turn inward and discover spirituality, from which the idea of only one god fell out, while other peoples simply used religions for their own ends. It could be said that there really is only one God, and that the different religions are just people arguing over what that God wants.
But it’s rather hard to associate monotheism with anybody other than the Jews, because while other nations obviously believed in the superiority of their people, their culture, and yes, their god, it’s hard to find a group of people that really and truly believed that the rest of the world was just worshiping rocks.
Not all Jews believed this, there was a thriving spiritual ecosystem of angels and demons, possibly inherited from Canaanite religions. It’s written in the New Testament that Paul believed pagan deities to be demons.