The Saudi Royal Family simply do not care and walk around with impunity. They thumb their nose at the law and the world order and think they deserve to do whatever they want. This is exactly the same as the Khagoshi execution where overwhelming evidence and implication, but, play naive and put on a big sham investigation. Just how when Russian agents poisoned the Skripals and said they were their to view a church steeple.
Of course, the nation that the Saudi's rely on for aid and military hardware could pressure them. But that would require some minimal commitment to human rights and a free press. And no personal desire to silence criticism from the WaPo by it's president.
This does seem the most likely, as hard as it is to believe. I guess when you have hierarchies based on blood rather than competency, this is what you end up with.
