I know this is too late but I'm gonna answer it nonetheless.

1_The first misconception about your question is that even before Mongols, Iran was nomadic in nature the Seljuks and Ghaznavids and even the Tajik Ghurids had nomadic origins even way before than that in the famous Samanid empire and compared to the ones you mentioned especially the likes of Safavids and Qajars they were perhaps even more nomadic.

2_ the other parts of the world like China you mentioned wasn't excluded from this the Qing Conquest of China might be a tricky one since Manchus who weren't Chinese in origins weren't nomads as they were sedentary people but their culture and ethnic background was viewed in the eyes of Han Chinese as a "barbarian" and the Russians successfully managed to contain the nomads but their forces were still consisted of the same nomads in fact Peter the Great of Russia was believed to have Tatar ancestry from his maternal side and Cossacks who later became the elites of Russian armies were nomadic in both lifestyle and origins.

3_ the idea of calling Iran turkified is kinda vague and inaccurate as historically it was the opposite, the main culture of Safavids and Qajars along with short lived Afshars unlike their old predecessors like Seljuks who had created a hybrid Turco-Persian culture was already transitioned to the fully Persian culture as historians argue that the reign of Abbas II of Safavids is believed to be the transition of Turco-Persian culture into Persian culture in its complete form this was natural since many of these dynasties who had nomadic origins, weren't nomadic anymore, as Abbas II was responsible for disbanding of nomadic Qizilbash which would later get replaced by Ghulams and Tufagnchis as part of centralization of military that stoped the reliance on nomadic tribes for recruitments this was later continued by Nader Shah of Afsharids who would replace the Qajar tribal cavalry men with Sawaran of Khorsasn which was created based on Mamluk cavalry in Egypt as part of his military reforms if we compare the Safavids to the dynasties of their counterparts who existed at the same time with them, the Qing and Tsars of Russia, we see that perhaps they were less nomadic compared to the Chinese Qing who would later in 19th century get more interested in Inner Asia and nomadic cultures of that place that was part of reverse cultural-transition of Qing as the result of growing tensions with the Han Chinese subjects along with the growing interest of Manchu language among the elites and the Russians on the other hand by the time Safavids started to get rid of Qizilbash forces, Russia was still heavily reliant on nomadic forces of Cossacks in their military that would continue to exist up until 18th century.

4_ like I mentioned before some of these dynasties weren't nomadic in origins the Safavids while being Turkic in lineage weren't exactly nomadic to be explicit despite the fact that they had nomadic Qizilbash on their back and were their main supporters, the founder of the dynasty Sheikh Safi Ardabili was a simple Sufi sheikh and their recent ancestors notably Sheikh Haydar who was Ismail's father wasn't tribal or nomad as he was a religious leader in the city of Ardabil that was a form of imamate, this isn't surprising since Safavids were a religious order at first that turned into a royal dynasty and a political entity and the next thing we should consider is the idea of "Iran" dynasties like Aq Qoyunlu didn't form "Iran" as an entity as they didn't control most of areas of the Greater Iran region since their rule was mostly concatenated in western regions in Zagros mountains and Mesopotamian which was their base despite the fact that Uzun Hassan called himself Shah of Iran and Persia, Iran didn't form and exist yet at that time since it was splited between Timurids in east and Aq Qoyunlu in the west, now back at Timurids, the Timurids despite being Persian in culture as it's clear by their later Mughal descendants and having their state named Iranzamin weren't technically an Iranian state in the eyes of Persian subject back at that time and even now, the Timurids' capital was in Central Asia away from mainland Iran the Timurids rose to power by a devastating conquest of Tamerlame they only became an Iranian state when Shah Rukh became ruler and called the state "Iranshahr" and the capital changed to Herat but Shah Rukh's rule was at the end of Timuird dynasty and after his death it ultimately fell so Timurids weren't Iranian or part of Iran since most of their history wasn't with the exception of Shah Rukh and the idea of Tamerlame conquest was still fresh among Persian subjects that viewed it as "Aniran" even though its cultural transition made them fully Persian in their end.

5_ the nature of Iranian society and legacy of Sassanids in this regard might be good to mention as much as Iran was sedentary it was also nomadic even in pre-Islamic times the Parthians were even more nomadic than likes of Safavids, Qajars or Nader Shah their rulling class was consisted of tribal leaders and confederations "The Seven Great Houses of Iran" were nothing more than 7 tribes forming the aristocracy and rulling classes, the Parthian military was relied solely on tribal forces for recruitment and that was the main reason why they were never able to mobilize vast numbers of troops against Romans who were centralised in military even less compared to their Sassanid successors, now talking about Sassanids even after they rose to power the 7 great houses and reliance on nomadic tribes for mobilizing forces continued to exist in fact the most important reason why Sassanid fell to muslim scourge was Parthians disagreeing to give them troops the Sassanids counted on the nomadic cavalries of Parthains in their wars against Romans, Parthians dominated the military of Sassanids their most legendary Sepahbeds, Shahrbaraz, Bahram Chobin and Shahin who were all Parthians is a sign of that this perhaps would also bring us to Achaemenids whose military was dominated by Scythians and their commanders in a way that Arabs calling Perisans, as "Red Mustache" might also be a sign of that this brigns us to a one simple fact regarding the history of Iran : that Iran was historically consisted of two parts : nomadic military men and Persian bureaucrats, after fall of Sassanids and beginning of Intermezzo period, the Parthians gradually sedentarized and their culture transitioned into Persian as a self-assimilation policy of Samanid Empire which was created by Parthain elites before ultimately getting erased from the records of history since the Parthians were no longer nomads and their lifestyle became sedentary someone had to fill the void that grow deeper inside the military armies of Iran which was a direct result of that so the Samanids started importing Turkic slave soldiers from Central Asia to Iran which formed their military ranks and royal guards the most famous one was Mahmud Ghaznavi's father who was a high ranking military commander of Samanid Empire this process also resutled in conversion of Turks into Islam and the creation of Turco-Persian tradition by Turkic subjects that would later form the head of the state that brings us again to the already mentioned fact of history of Iran and it's scoial structure being consisted of two parts : nomadic military men and Persian aristocrats.