I think the most likely scenario is that russian soldier executed the POWs well before the crash, and are just saying they died in the crash to cover up their war crimes.
Sounds to me like Russians executed 65 POWs. Then in an unrelated event, a plane crashed. So Russia says the 65 war crimes were actually killed in the plane crash. Oh, and they also say this is all somehow Ukraines fault.
Russia wants NATO and other nations to feel that they could invade so the countries will start focusing on thier own defensive positions and stop giving aod to Ukraine. Expect to see a LOT of fake news and propaganda about this.
Those mountains? Nah, that place needs mining!