Research has several answers as to what caused the distinct syncretic (its modern expression is cultural Islam, as opposed to Middle Eastern and North African political Islam) Islam in Southeast Asia, that allowed the continuation and inclusion of elements and ritual practices of Hinduism, Buddhism and ancient Pan-East Asian Animism.
Unlike virtually all other "Islamised" regions like North Africa, Iberia, the Middle East and later India, Islamic faith in Southeast Asia was not enforced in the wake of victorious territorial conquests of unstoppable Muslim armies under the command of pious and charismatic warlords.