Early on in it's history, Manichaeism was the main rival faith to Christianity, but was consistently persecuted throughout history by the Sassanian kings.
However, around the time Christianity was gaining strength in Rome, Manichaeism was gaining strength in Persia under the tolerant king Narseh.
Suppose ʿAmr b. ʿAdi ends up converting Narseh, or he converts on his deathbed. I think it's plausible he could convert to a monotheistic faith as he already placed an emphasis in the prominent God in the Zoroastrian faith Ahur Mazda over others.
If Narseh converts, I believe that under Shapur II, Manichaeism could become an established religion, with nobles installing the unborn prince as King as they did OTL, but led by Manichaean religious authorities as opposed to Zoroastrian ones.
Under the Golden Age, Shapur II led the persecution of Christians in reaction to the adoption of the religion by their rival Rome, and in this TL he could promote the religion of Manichaeism as a rival monotheistic faith to the Romans and as the true Persian faith.
However, around the time Christianity was gaining strength in Rome, Manichaeism was gaining strength in Persia under the tolerant king Narseh.
Suppose ʿAmr b. ʿAdi ends up converting Narseh, or he converts on his deathbed. I think it's plausible he could convert to a monotheistic faith as he already placed an emphasis in the prominent God in the Zoroastrian faith Ahur Mazda over others.
If Narseh converts, I believe that under Shapur II, Manichaeism could become an established religion, with nobles installing the unborn prince as King as they did OTL, but led by Manichaean religious authorities as opposed to Zoroastrian ones.
Under the Golden Age, Shapur II led the persecution of Christians in reaction to the adoption of the religion by their rival Rome, and in this TL he could promote the religion of Manichaeism as a rival monotheistic faith to the Romans and as the true Persian faith.