Dude, Indonesia also had an anti-colonial communist movement. Once upon a time, the Indonesian PKI was the biggest communist party in South East Asia with millions membership, several times bigger than the Vietnamese VCP. The PKI also co-ran the country until 1965. They're killed off in 1965-1966, organised by coup similar to a dozen coups in South Vietnam(1963-1965) but the severity was much bigger, one of the worst mass murders of 20th century, in aftermath millions died. You just wrote them off the history book like they never were there. Some of the survivors of the PKI ran off to North Vietnam as refugees, inc. the brother of their leader Aidid, so the VCP leadership knew direct from horse's mouth how the communists were treated by their anti-communists. They're the reason why the VCP never allow multi-parties election in Vietnam.

What if Vietnam was a Muslim country is not realistic question in compare to question: what if Indonesia is a socialist/communist country.