A hook stuck to a wall can support a large mass if it is hung close to the wall compared to the mass suspended at a distance. Why is this so.
The factor affecting the ability of a hook stuck to a wall to hold on is the torque about the point it is anchored rather than the force acting downwards on the hook. The torque due to a force about a point is a function of the magnitude of the force as well as the distance of the force from the pivot point.
If a body is suspended from the hook close to the wall, the resulting torque is small as the distance of the point at which the force acts from the wall is small. As the body is hung farther away from the wall, the magnitude of torque increases for the same mass.
This is the reason why a large mass can be suspended close to the wall with the hook continuing to hold on.