How did Islam become Persianized?

In a Nutshell: The Islamic civilisation adopted the permissible traits of all cultures that it subsumed including those of Persia. This was part of its universal appeal, destroying that which was objectionable and retaining that which was acceptable, even encouraging it to flourish. Muslims or the Islamicate as opposed to Islam absorbed material culture from various indigenous populations that were encountered. The Islamic revelation however remains unique and universal amongst all Muslims. Conquest of Persia If Muslims had failed in their campaigns in the Iranian Plateau, and instead, the Byzantine Empire had succumbed to their onslaught, then what would the world be witnessing? No doubt it would be Muslims whose culture was derived from the Europeans. The Arabs were culturally inferior to both the Byzantines and the Sassanids. Since the Sassanids collapsed they were integrated into the Caliphate along with their culture. The Persian cultural infusion arose from a massive influx of Persian poets, scribes, artists, engineers, architects, historians, writers and scholars seeking employment in the service of the Muslims, losing employment from their native kings who abruptly ceased to exist. The continued successful resistance of the Greek Byzantines pushed the Muslim culture into the arms of Persians, resulting in a conscious rejection of styles of the hated Greeks.  The Islamic civilization always sought to differentiate itself from others as part of identity formation from the prophet's era. It always sought to present images of complete divergence, showing their civilisation to be distinct to others, displaying this in everything from the clothes they wore to the weapons they used, to the vessels they drank from. The difference between Christianity and Islam is in effect a renewed version of the difference between the Greeks and the Persians. Persian Scholarship The Persians were also revolutionary in terms of theology and intellectual development of Islam. Medieval Persians scholars were large in number ranging from the likes of al-Tabari whose Qur'anic exegesis played a vital role in the development of Islam theologically, al-Imam al-A'zham Abu Hanifa founder of the largest legal school of law and al-Ghazali, a giant in theology and philosophy. Among the major Persian Muslims one can mention, the following are well known: Nasai, Abu Dawud, Bukhari, al-Bayhaqi, al-Tirmidhi, Hasan Al-Basri, Abdul Qadir Jilani, Hasan Al Basri and many others. The Persians provided the intellectual stimulus that gave Muslims the drive to develop their own sciences if only to respond to other civilisations. A case in point was the Kalam movement in response to the influx of Greek philosophy. So a Persian outlook on Islamic scholarship emerged with many of authoritative Islamic texts written in Farsi, especially under the Abbasid Caliphate which had a Persian bloodline.  Abu Huraira reported: We were sitting in the company of Allah's Apostle (may peace be upon him) that Sura al-Jumu'a was revealed to him and when he recited (these words):" Others from amongst them who have not yet joined them," Then a person amongst them (those who were sitting there) said: Allah's Messenger...! But Allah's Apostle (may peace be upon him) made no reply, until he questioned him once, twice or thrice. There was amongst us Salman al Farisi (The Persian). The Apostle of Allah (may peace be upon him) placed his hand on Salman and then said: Even if faith were near the Pleiades (The furthest Planet), a man from amongst these (Persians) would surely find it. (Book 031, Number 6178)  Persian Influences through Expansion Islam further expanded into Eastern Europe to Central Asia under the guise of Turk-Persian Rulers, which have given Islam a Turkish-Persian flavour there. The likes of Ottoman Caliphate, Seljuk Sultanate, Mughal Sultanate, Muslim Mongol sultanates, all of them, were very 'Persianate' in nature and essence. " Virtually all civilisations… were limited to one region, one culture and usually one race. The Islamic culture of the Middle East was the first that was truly international, intercultural, interracial, in a sense, even intercontinental, and its contribution—both direct and indirect—to the modern world is immense."(Bernard Lewis) Conclusion For the purpose of discussing cultural adoptions, a distinction must be made between material culture and intellectual culture. Material culture includes architecture, culinary arts, fashion, technology, etc, i.e. all the things that are not ends in themselves but means to ends and therefore can be used by anyone. Intellectual culture refers to ideology, a viewpoint about life, societal structure and laws, etc which is far more important and significant in its influence over a civilisation than material culture because it defines the direction and the ends of the civilisation. Therefore, 'Muslims' or the 'Islamicate' (rather than Islam itself) absorbed material culture from various indigenous populations, not just Persia. The Islamic civilisation remained unique and universal between all Muslims.