Why Can’t The Boeing 777X Be Powered By Any Other Engine Type?

TheBoeing 777X is soon to enter the market, and it will be exclusively powered by the GE Aerospace GE9X turbofan. But why is it exclusively powered? After all, the original Boeing 777 series was optionally powered by the Pratt & Whitney PW4000, the Rolls-Royce Trent 800, and the General Electric GE90. However, the second-generation successor family (777-200LR and 777-300ER) was then exclusively powered by the GE90.