A favorite word sixty years ago was "inferiority complex". When we first mature physiologically, we have not yet been able to test our power of achieving our goals, and we often are timid about testing our powers, for fear of a rebuff. So it is safer to admire from a distance.We often first select someone unattainable, because that means we have an excuse for not making an advance. But I have no idea why this was called "a crush".