The way I see it, there are three likely possibilities. There was something or someone on that plane that A.) at all costs, could not be allowed to land in Beijing or b.) that, at all costs, needed to be secured by Beijing. Less likely, though certainly equally worthy of consideration, is C.) a government or organization that needed to secure a Boeing 777 by theft in order to use it later to infiltrate someone's airspace, most likely US airspace, with some kind of a weapon, a weapon big and bad enough to justify a conspiracy of this magnitude.
I keep thinking Iran needed techs for its nuclear ambitions, because what few they had met a sudden termination.
If they cannot get them willingly then just capture a whole herd of them.
Whatever its takes to eradicate Israel. I would believe the pilot was under duress or offered a large sum to deliver his human cargo of tech experts to Iran, does anyone know WHERE his family is, are they hostages?