The word asura carries a genuine shift in meaning across the span of Vedic and later Hindu literature, and the shift is worth tracing before treating the term as a simple label for demons. In the earliest hymns of the Rigveda, asura functions as an honorific, lord or powerful one, and is applied without any negative charge to major deva figures, Varuna most prominently, alongside occasional use for other beings of great power regardless of their later alignment.
Only over the course of the Brahmana literature and into the Puranas does the term narrow and darken, coming to designate a fixed class of beings opposed to the devas, often described as the offspring of Kashyapa by his wife Diti, making them cousins to the devas born of the same father by a different mother, Aditi. This kinship framing matters to how the tradition understands the rivalry: it is not a war between essentially different kinds of being so much as a family conflict over inheritance, precedence and the sacrificial offerings that sustain cosmic order, which is part of why individual asuras, Shukracharya's devoted following among them, are portrayed with genuine nobility, learning and religious discipline rather than as uniformly monstrous.