Jacob Grey is that kind of person. Reckless and unpredictable.
This is coming from the guy who just stole weapons from the military HQ of a powerful foreign country. It's also coming from the guy who is about to give the leader of said country booby-trapped versions of said weapons under rather guise of fixing an honest mistake. It's also coming from the guy who knows that this will most likely make him an enemy of said powerful country, possibly sparking the same devastating war that irreparably changed his original world.
All because he doesn't want to give up on a few extra relics.