So I think to answer this, we first need to find out what Hinduism is. I think that outdated scholarship, post-colonial nationalism, and vague pop spirituality have presented a distorted perception of Hinduism as a whole, giving the impression of a unified religious practice, this is not at all the case. While I think everyone who has some awareness of Hinduism knows it is diverse, the extent of that diversity is often understated. When we speak of religions, we often simplify it to certain ones, take for instance Christianity. Anthropologists and scholars of religion sometimes talk of Cbristianities as the practices and beliefs of one Christian community might be radically different: take Big Tent Evangelicalism and Roman Catholicism for instance. Hinduism is even more diverse than that.

Largely, Hindus typically belong to a few groups which are largely non-exclusive in terms of what practices are incorperated. There are Shavists, Vaisnavists, Smartists, Shaktists, and a few other smaller groups. Largely, these define who or what is seen as the pricipal diety and which Puranas are considered orthodox. However Hindu philosophy is grouped into different schools, the largest of which is Vedanta which is further subdivided into advaita, dvaita, and vishishtadvaita depending on how the relationship between brahman (a monoistic pricipal) and other things is viewed.

However these are all non-exclusive and practices between philosophies and dieties are adopted fairly freely. However, this free adoption does not indicate a unity of practice or opinion. Rather, there is sometimes a deep divide within different practices within Hinduism, to the point where Hinduism in Karnataka looks dramtically different from Hinduism in Punjab. Heck Hinduism is dramatically different in Nepal and the neighboring Uttar Pradesh. In Nepal, Hinduism has taken influences from Newar Buddhism, Tibetan Buddhism, Chinese religion, and native religions which are absent (or at least less present) in Uttar Pradesh and thus the festivals and practices are dramatically different.

Anyway, so Hinduism is diverese, but that doesnt really give you a proper explantion. For that we have to look at the history of Indonesia. Indonesia has been an important part of the silk road since early antiquity, presenting one of the key points alonf the maritime route between East Asia and India. Because of that, Indian contact with Indonesia was early and significant. Hinduism and Buddhism first arrived around the 1st century BCE and by the 6th century, Hinduism and Buddhism had fused with the native religions and become the dominant religions on the archepeligo. By the 7th century, the powerful maritime empire of Srivijaya dominated the archipelago and strengthened Buddhism on the island, bringing missionaries and monks from India and building monuments. After the 11th century, conflict between the South Indian Cholas and Srivijaya led to the dominance being destroyed and allowed the rise of the Javanese based Majapahit empire who dominated the archipelago.

The Majapahit kings promoted a syncretic religion that conciously fused Buddhism and Shavism. While the extent that this was adopted is unknown, the importance of Buddha in Balinese Hinduism attests to some success in the mission. The religion in Majapahit had divirged significantly from the Hinduism exported there and specific texts and traditions emerged.

As Majapahit rose, Islam arrived and some of the vassal kings began to adopt it and new economic opportunities were availible to converts. The Islamic kings, both foriegn and native converts, challenged the Majapahit kings. However, it wasn't until the 15th and Sixteenth centuries that Hinduism and the Majapahits were pushed to east Java and Bali. Weakened by civil war and raids, Islamic kings managed to overthrow the Majapahits and ended Hindu control. Bali and isolated parts of East Java remained Hindu stronholds but mutual influence was exerted on Hinduism and Islam.

Anyway, The major difference between Hinduism in Indonesia and other parts of the world is that it has been there an very long time while the newer communities are, well, new. Hinduism has long since assimilated into Indonesian culture to the point where until recently, many nominally Muslim Indonesians retained some Hindu and Buddhist practices while communities in South Africa or the US are still to an extent foriegn. Furthermore, these new communities retain a connection to India and their home communities that was impossible even 100 years ago, so practices don't diverge as much.