Zanzibar was part of the Sultanate of Oman until the late 19th century and there was always a large amount of cross-ocean trade between Swahili Coast, the Safavid Empire, the Ottoman Empire, the Omani Sultanate, and the Gujarat Sultanate and the Mughals.
There was an interesting book I found once at a used book store that specifically translated Gujarati language Ismaili papers and sermons brought by traders that spread Islam into SEA. Sadly I didn't get around to buying that book, but could probably find it.
That said, there was a decent amount of Shia polysterization as well in SEA that ended up getting mixed and merged into Sunni Islam due to political influence. (If interested in sources please reply to this thread because I'm lazy and don't feel like doing extra work unless there is actual interest)
Wasn't the Persianization of Sunni Islam due to the Delhi Sultanate and Mughals who had Persian cultural links?
And do we know which Sunni Muslims mostly spread Islam to SEA? From what I understand Gujarati Muslims were heavily involved but with no reference to the specifics of the communities. My DNA also surprisingly showed substantial persian-like ancestry.
On the religious side, a number of Babas and Gurus revered by Punjabi+Pakhtun+Koshur Hindus and Sikhs were Persian Sunni refugees or emigrants. For example, Lakhdata/Sakai Sarwar/Syed Ahmad Sultan and Mohiuddin Chishti/Khwaja Gharib Nawaz/Khwaja Baba are from Abbasid/Persianate Baghdad and Sistan respectively, though there are tombs for hundreds of Pirs littered all over Northern India. In fact, in Iran there are Fakirs/Darvishs as well in the same manner and motif as you'd find among the Hindu and Sikh community in South Asia.
And ethnicity wise, I'd honestly not be surprised. Gujarat/Sindh/Punjab/Pakhtunkhwa/Balochistan/Kashmir all literally neighbored ethnically Persian regions like Sistan and Khorasan.
Modern Shia and Sunni Islam is heavily modernized/reformed in the 19th century due to the impact Imperialism had on the Ottoman, Iranian, Bukharan and Mughal spheres. The same thing happened to modern Hinduism with the influence of revivalist and reformist movements like Arya Samaj and Sarvarkar and modern Sikhism with the Akali Dal. While the older traditions still persist in smaller towns due to the time capsule effect, those traditions and folklore are slowly dying away. Such is society I guess.
For the SEA standpoint, it was a mix of Gujarati, Marathi, and Tamil Muslims. I don't have names off the top of my head (largely due to my linguistic and cultural ignorance of those regions). If you're still interested reply to this thread and I can spend some time digging into it. It's somewhere in my notes from when I was attempting to write a thesis on Subaltern Religious Traditons before I pivoted to Tech Policy and Econometrics.
From the DNA results I've seen, I believe most of the Iranic like ancestry in these regions is older and from the BMAC / Oxus civilization. Some Syed groups have some recent middle eastern ancestry but substantial amounts are absent from most communities. Coastal South Gujarat seems to be an exception with some Sunni Muslims farmers having substantial foreign ancestry.
> Modern Shia and Sunni Islam is heavily modernized/reformed in the 19th century due to the impact Imperialism had on the Ottoman, Iranian, Bukharan and Mughal spheres. The same thing happened to modern Hinduism with the influence of revivalist and reformist movements like Arya Samaj and Sarvarkar and modern Sikhism with the Akali Dal. While the older traditions still persist in smaller towns due to the time capsule effect, those traditions and folklore are slowly dying away. Such is society I guess.
Our Islam changed quite a bit during this time due to Wahabbi/Deobandi preachers coming to Gujarat. Hindu practices and consumption of alcohol were heavily frowned upon afterwards.
I'd definitely like to read more about the topic, but no big deal if it's hard to find the sources.