There was a political cartoon of the time - “Domino Theory Revisited”. It showed the Russians, Chinese, Vietnamese, Laotian and Cambodian leaders pushing their giant dominos on top of each other and leaving Thailand standing on the side watching bemused and untouched. Remember that Vietnam also went to war with China… The western war hawks had always claimed that communism had to be stopped in Vietnam lest it proceed to Cambodia, Thailand, then Indonesia, etc. Not quite.
This is the classic “reign of terror” phase of the revolution - any revolution. The larger consensus group that may have thrown out the original regime becomes increasingly more strident with its ideology. The more shrill the screams of ideology become, the easier it is for the various factions to pick off their rivals by claiming they were insufficiently faithful to the ideals of the revolution. Generally, toward the end, the revolution tends to consume its own; as the more moderate leaders are picked off, the tone of leadership gets more and more irrational.
(One of the most surprising aspects of history is - why did the American Revolution manage to escape this phase?)