I'm not saying that Boeing had him assassinated, but I sure wouldn't put it past them. They've already shown themselves to be perfectly willing to sacrifice human lives for increased profits.
There's a fairly short list of companies I could see doing something like this, and Boeing is on that list. I could see Boeing, Lockheed Martin, Exxon Mobil, JPMorgan Chase, McKinsey, ...
Every single one of these companies were already pulling in a massive amount of wealth but they knowingly killed people just so that they could make even more money. They all put additional profits over human lives. There is no reason to think they wouldn't put a bullet into someone's head if they thought it would make them more money. In many cases it would have been much more humane if they had.