Before the 20th century and the 1960's Islam in Indonesia was pretty weird. Lots of syncretism ranging from south east asian shamanism to stuff like Wetu Telu where they only pray three times a day and ignore 2 of the 5 pillars. And then you have places like Yogyakarta where the Sultan has his own sea goddess girlfriend and gives sacrifices to the local volcano spirits. Some of those things survived to the modern day as traditions.
Did no scholars from modern day Saudi Arabia or the Ottoman empire take a trip to Java and come back to complain that half the island was full of heretics?
Did no scholars from modern day Saudi Arabia or the Ottoman empire take a trip to Java and come back to complain that half the island was full of heretics?