Either they really have no idea or they’re lying through their teeth. I think it’s the later. I think they know exactly what happened.
They had to come up with a story to get those relatives out of the hotel.
My thinking it was freakish series of events from a combo of possible criminal intent(less likely by the day if the info is true) leading to and/or just a tragic failure of the system(s) of the plane(possibly cascading series). I hope my guessing make some sense.
I think you are sadly right about the reason.