Jewish gnosticism also existed, maybe even before Christian gnosticism. Arguably Christianity grew out of a Jewish gnostic movement. I think that some Jewish sects differentiate between the gods “El” and “Yahweh” from the old testament and they consider “El” to be the demiurge and “Yahweh” to be the god of light.

It would make sense that this occurred after some heavy cultural borrowing from the zoroastrian Persians who had a dualistic cosmology