Under normal circumstances once the bees detect one of those monster hornets hundreds of them will gather just inside the entrance to the hive, waiting in ambush. Once the Hornet enters, hundreds of bees will pile onto the hornet, preventing it from moving. At this point, the bees will use their muscles normally reserved for flight to raise their body heat and produce more CO2. The most of the bees are able to withstand this sudden leap in temperature and CO2, but the Wasps cannot, causing them to suffocate. This leads me to believe that these bees were inexperienced in the art of wasp combat, likely from some foreign nation