The number is astronomical before it is theological. Seven bodies move against the fixed stars as seen from earth, the moon, Mercury, Venus, the sun, Mars, Jupiter and Saturn, and a cosmology of nested spheres carrying them was standard across the ancient Near East and the Hellenistic world. Seven heavens is that model with the ceiling raised.
What Jewish sources add is an itinerary and a visitor. The Hekhalot literature describes an ascent through palaces, each with guardians who must be answered correctly, and the danger of the attempt is emphasised rather than minimised. Second Enoch takes Enoch up through the levels and describes what is stored at each. Later rabbinic material names the seven and assigns each a function, from the curtain drawn back every morning to the highest, where the throne is.
Paul writes of a man caught up to the third heaven, and assumes his readers know that the phrase implies a structure with more above it. The Islamic account of the night journey uses the same architecture, with a prophet met at each level. Three traditions with different theologies share one floor plan, and the floor plan came from astronomy that all three inherited and that none of them invented.