If one wanted to destroy the Islamic State, they could make sure it wouldn’t be able to negotiate for ransom and that it was seen even by many radical Muslims as using methods beyond the pale. By killing their hostage in a particularly brutal manner while still “negotiating”, the Islamic State has accomplished both as well as provoking the bloodlust of the pilot’s tribe in Jordan.
I wonder if an intelligence agency (say Mossad or even Jordanian mukhabarat) was able to infiltrate (or even create) a particularly brutal faction of the organization and cause it to do things that generated extremely bad publicity.