Not being able to test alternate universes sans Instagram acquisition doesn't mean that it's not impossible to tell whether a CEO is good or not, you just have

Not being able to test alternate universes sans Instagram acquisition doesn't mean that it's not impossible to tell whether a CEO is good or not, you just have to make a qualitative argument for why they are or not. Buying IG was a good move because it has paid back Facebook's shareholders multiple orders of magnitude. Isn't the goal of the CEO to steward the company and to make shareholders returns (wether public or private)?