What makes a crane so strong?
Cranes are built using a structural technique called a truss which is characterized by looking like a series of triangles connected together. That structure prevents the members from having to resist any bending loads. All of the truss members experience only tension and compression, no bending. That is an extremely efficient structure which is why they can be so strong without being monstrously heavy. Or if you prefer the short answer, engineers make the crane so strong.
