Both performed as designed.
The lenses are pre built with a weak spot at the mount, so if a lens is dropped with the camera it will snap and not only protect the mount on the camera body but to reduce damage if the camera bounces with the lens intact (being font heavy with a lens its more likely to bounce with the cameras weight directly onto the glass element. The lens mount is also designed to be replaceable to protect the glass element, cheaper to replace the mount than the glass.