As I understand, Boeing wanted to use larger engines because larger, hotter engines burn less fuel. But increasing the diameter of the engine ordinarily means raising the wing in order to accommodate it but that would make the plane incompatible with existing infrastructure (such as jet bridges) at airports. For that reason Boeing positioned the engine forward on the wing instead of raising the wing.
Don't newer Airbus planes also have larger engines? How did they maintain compatibility with existing airport infrastructure while accommodating a larger engine?