alt Hacker NewsSufis were meant to propagate that Islam is syncretic to get people to convert wherever they went. Once Islam got a critical mass of converts (15-20%), Islamic invaders would have the necessary internal support to invade and destabilize the Kingdom.
This is literally how Islam got to places in Asia and spread. It was through Sufis who acted as initial points of contact.
> A lot of these traditions are much more flexible than whatever is the dogma or institutional version of the time suggests.
This is only so when it comes to missionaries in each religion. Be it Evangelists saying Vishnu is Avatar of Christ (we literally have Christ idols shaped like Vishnu with multiple arms and sitting on a lotus in a Church in India), Sufis singing Krishna is same as Allah or heck even ISKCON claiming Christ is an Avatar of Krishna /Vishnu. That does not make "traditions flexible". It's just a cheap tactic to increase followers/harvest souls. These converts are typically fluid in their own convictions and can easily be swayed one way or the other based on reasons unconnected to the Religion/Dogma/Philosophy itself. Reasons could range from political, monetary to finding fame/popularity within a new sect/group/cult/ideology.
Very few are seekers of Truth.
>That does not make "traditions flexible". It's just a cheap tactic to increase followers/harvest souls.
That's not mutually exclusive. You're certainly right that religions spread this way, but it's also what they become. Christians today are Pauline Christians more than anything else. The abolition of circumcision and dietary restrictions, household code, 'render unto Caesear' etc were obviously tactics to convert Gentiles, but once you had all the gentiles, you had genuinely altered what the faith is. They never went back to the radicalism of Jesus.
Buddhism is also an interesting case. By the start of the 19th century there wasn't strong Buddhist practice in India. When it was rediscovered it was heavily shaped by China, Tibet and Japan and had done a round about turn.
Same with modern Evangelicalism and Catholicism. Very successfully spread through indigenous cultures in LatAm and Africa but now the influence goes the other way, with real impact on the churches, just look at the last two popes. I don't think this deserves to be categorized as cheap tactic, that's very much what religion is.