ISIS claimed they shot it down initially. That tells me they don’t know what happened. I’m guessing a lone wolf Jihadist luggage handler.
If not ISIS than someone who is sympathetic to them because if ISIS themselves did the bombing they would never have said they shot it down they would have said they planted a bomb so I think you are right..some Jihadist who is sympathetic to ISIS did this but now we must ask, how did they get the bomb on board, inside job or is Egyptian Airport security in the toilet
I think the statement just said they “brought it down” probably to keep the claim deliberately vague but the accompanying fake video was of a shooting.