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.
Not defending the US bombing of Cambodia, but it's a bit misleading to bring this up without quantifying that there's at least an order of magnitude difference in fatalities between the two.
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].
They can not be so easily delineated. Carpet bombing = loss of homes and farmland = general socioeconomic crisis = extreme political instability. And very much by design.
I agree, I just was pointing out that the death toll from the bombing wasn't even the worst consequence. Pol Pot was, in effect, the largest bomb dropped on Cambodia.