As more of the French trying to further take over the region and losing badly. Their entry was the fault of their king trying to play both the khmer rouge and the US as allies until the US started carpet bombing Cambodia because Khmer Rouge were supplying arms to the Veitcong and then the king went fully on Khmer Rouge side where he was forced out (because they thought he was an idiot for playing both sides and still getting them bombed) and Pol Pot took over. Eventually when the war ends, Pol pot flees (or sent his kids) over to Europe while Khmer Rouge has a fighting retreat into the jungle or surrenders. After the genocide they lost so many people the ones left basically said they had to forgive Khmer Rouge because otherwise they would be down to less than 1/3rd of their original population. Still some khmer Rouge sympathizers today, still lots of unexploded ordinance, and they’re still finding remains from various mass Graves.

They didn’t seem to have any hard feelings towards any of the foreign nations which I thought was odd but was explained to me as part of their belief system that they have to offer forgiveness and hope people can change for better. (It’s been a few years)