I answer a similar question here tying it to Sasanian royal ideology. Other approaches are possible, including for example noting the role Zoroastrian nobility played in the 'Abbasid revolution and the importance of Persian scholars like al-Tabari to Quranic exegesis and jurisprudence (where Sasanian influence on early Islamic law and court ideology is obvious).

Naturally, feel free to ask any followup questions.

Hey there,

Just to let you know, your question is fine, and we're letting it stand. However, you should be aware that questions framed as 'Why didn't X do Y' relatively often don't get an answer that meets our standards (in our experience as moderators). There are a few reasons for this. Firstly, it often can be difficult to prove the counterfactual: historians know much more about what happened than what might have happened. Secondly, 'why didn't X do Y' questions are sometimes phrased in an ahistorical way. It's worth remembering that people in the past couldn't see into the future, and they generally didn't have all the information we now have about their situations; things that look obvious now didn't necessarily look that way at the time.

If you end up not getting a response after a day or two, consider asking a new question focusing instead on why what happened did happen (rather than why what didn't happen didn't happen) - this kind of question is more likely to get a response in our experience. Hope this helps!

Hello,

In regards to your question, firstly, Zoroastrianism did not die. There are still about 200,000 people practising; it's not fair to consider their beliefs dead. Secondly, the Early Muslim empire did not entirely dismiss the beliefs and cultures of others. Instead, they have adapted to Zoroastrianism while adding their own culture and religion. A simple example of this could be derived from material cultures, such as coinage. You can see from the following link that until the reign of 'Abd al-Malík (d. 705) Zoroastrianism symbols were still used in coins.

https://www.davidmus.dk/en/collections/islamic/dynasties/umayyads/coins

Another example of Islamic adaptation of Sasanian culture and Zoroastrianism beliefs is through the adoption of their policies and social systems. Examples of this can be derived by studying the taxation and social class of the early Muslim community in al-Sawad (Iraq/Iran). The amount of tax and the methods of extracting tax remained unchanged following the Islamic conquest. You can see Daniel C. Bennett "Conversion and the poll tax" works for more info on the matter.

While the core faith of Zoroastrianism had been dismissed since they were not considered people of the book (Christianity, Judaism, and Islam), a lot of their influence remained and merged with the early Islamic society.

Hope that answers your question! ^^