Pol Pot and his government was responsible for the death of 1/4 Cambodian population in a short amount of time, not counting deaths from neighboring countries. A lot of Cambodians migrated to Vietnam (including the author of this wonderful piece). The history about this period is interesting if you're looking for a good read. It's not being widely taught, even during Vietnamese K12 education. https://en.m.wikipedia.o…
Not defending Pol Pot, but attributing mass death solely to his regime is a bit misleading when it corresponded with a hostile foreign power carpet bombing the region with hundreds of millions of bombs, many still unexploded, over a decade or so.
What's noteworthy, though, is that the Khmer Rouge was fighting against the puppet government installed by the hostile foreign power; and that the king displaced in the coup sided with Khmer Rouge as a result, which meant quite a bit in terms of support.
That's to say, the Pol Pot and the Khmer Rouge would have not been there, if not for the US meddling. You don't have to take my word - take it directly from them[1].
[1] https://www.reuters.com/article/us-cambodia-rouge/khmer-roug...