The most prominent Deva/Daeva were highly martial beings, such as Indra and Agni of the Rgveda. Among the fundamentals of Zoroaster’s teaching appears to have been the idea that martial prowess could not be inherently virtuous. This is evident in e.g. the “Zoroastrian Creed”, Yasna 12, which is usually thought to date to the earliest days of the faith (See e.g. Boyce, 1992, p. 84 and pp. 104), up to some additions and linguistic shifts. A few verses illustrates the point well:
I choose the good Spenta Armaiti for myself; let her be mine. I renounce the theft and robbery of the cow, and the damaging and plundering of the Mazdayasnian settlements.

I want freedom of movement and freedom of dwelling for those with homesteads, to those who dwell upon this earth with their cattle. With reverence for Asha, and (offerings) offered up, I vow this: I shall nevermore damage or plunder the Mazdayasnian settlements, even if I have to risk life and limb.

I reject the authority of the Daevas, the wicked, no-good, lawless, evil-knowing, the most druj-like of beings, the foulest of beings, the most damaging of beings. I reject the Daevas and their comrades, I reject the demons and their comrades; I reject any who harm beings. I reject them with my thoughts, words, and deeds. I reject them publicly. … I pledge myself to the Mazdayasnian religion, which causes the attack to be put off and weapons put down; [which upholds khvaetvadatha]*, Asha-endowed; which of all religions that exist or shall be, is the greatest, the best, and the most beautiful: Ahuric, Zoroastrian. I ascribe all good to Ahura Mazda. This is the creed of the Mazdayasnian religion.

*Highly likely to be a later insertion or even an incorporated gloss, close-kin marriage is otherwise not attested in early Avestan literature
To understand why raiding and plundering glorious heroic warfare would be celebrated in Sanskrit tradition but eschewed by Zoroaster and his early followers, we must consider the prophet’s time and place. It is virtually unanimously accepted on linguistic grounds that Zoroaster lived somewhere in the east of Greater Iran, some time before c:a 1000 BC, with Boyce’s suggested time of the 13:th century being the most commonly cited. However, exactly where he lived is considerably more controversial. Per the archaeological analysis of Grenet (Wiley-Blackwell Companion, 2015, pp. 21-30) the oft-suggested Bactria-Margiana complex would have been too urbanized to be reflected in the absolute pastoralism that early Avestan material presents us. On the other hand, Almut Hintze (ibid., pp 31-39) argues that this area, or perhaps Sistan, is where linguistics would place us. Textual analysis doesn’t get us much further. This puts us in the awkward position of having no two independent methods that lead us in the same direction.

A suggestion Boyce makes is that Zoroaster may have belonged to a tribe that was particularly poor, isolated and/or traditional in its lifestyle, which in my view is the best way to reconcile the sparse evidence we have. This then helps us understand why the proliferation of Bronze-age chariot warfare would have been particularly distressing to him and his tribe, and a threat to their way of life. To understand why this threat would be identified with Daeva like Indra, we can turn to Sanskrit tradition, Rv 4.42. Unfortunately this hymn is difficult to read and contains lines which appear to be later insertions that identify Varuna with Indra. However, we may excise a few of the couplets that appear to contain a core tradition that contrast Indra with the Asura Varuna:
Varuna:
Lordship (raṣtṛam) belongs indeed to me, the eternal sovereign (kṣatriyasya), as all the Amrta acknowledge to us//The Deva obey and follow the will of Varuna, I am the king (raja) of men’s most lofty refuge

I am King (raja) Varuna, I was granted these primordial celestial powers (asuryani)//The Deva obey and follow the will of Varuna, I am the king (raja) of men’s most lofty refuge

I let the dripping waters rise up, through rta I uphold the sky//Through rta I am the lord who rules through rta. [NOTE: I base the translation of this line off Boyce, I have seen other varieties of it, such as “By Law the Son of Aditi, Law Observer, hath spread abroad the world in threefold measure”, which looks Vishnuist, so there may be variants.]
Indra:
Men who drive swiftly, having good horses, call on me when surrounded in battle// I provoke strife, I the mighty Indra – I whirl up the dust, my strength is overwhelming

Such are my deeds. No divine (daivyam) power can control me, the invincible one//When draughts of soma, when songs have made me drunk, then both the unbounded regions frighten.