It all leads to one God

No matter what someone believes, whether their worldview is polytheistic, monotheistic, henotheistic, or even tied to ideas about aliens and extraterrestrials, many traditions still point back to a supreme source or highest divine authority. That does not mean every religion teaches “one God” in the same way, but it does show a repeating pattern across cultures. In Hindu thought, Brahman is often understood as the supreme reality behind existence. In Mesopotamian religion, Anu was viewed as the sky god and one of the highest divine authorities, even though the religion itself was polytheistic. In Yoruba tradition, especially among the Yoruba of Nigeria and surrounding regions, Olodumare or Olorun is understood as the supreme creator above the orishas. So the better argument is not that every belief system is strictly monotheistic, but that many ancient and modern belief systems recognize a highest power, supreme source, divine order or supreme being behind everything.