Aceh is a weird exception in Indonesia. They were only intregrated into Dutch Indonesia in early 20th century and always had a tenuous relationship with the various Malay states and a very strong political and cultural connection with Turkiye (being a vassal of the Ottoman Empire at various times in it's history).

Also, the parts of Indonesia I've been to (mostly Java) feels much less "Islamic" on the ground than Malaysia. Yes I see hijabs fairly often, but to me at least, Islamic motifs seemed much more prominent in Malaysia and even Singapore than Java.