It would be useful to predict things like earthquakes and tornados. Gambling on what politicians and celebrities will do is not science it's degenerate court gossip.
What makes you believe this? The performance of economist/sociology experts using game theory to make predictions has been worse than a coin-flip up to this point. It also has done enormous damage.
This is also ignoring that game theory of partisan games breaks if any of the participants knows what the other will do. Is one of the more famous ideas.
To that end, if you want to predict what someone will do, more often than not you are best looking at their experience doing said thing.