Chains snap because they possess no associated stress transfer conduits. With steel rope this is catered for by multiple strands which transmit these stresses. Should excess load or abrasion begin to take its toll the rope will begin to fray and which process is not instantaneous but gradual.
With a chain there is a single point (at the top of each loop) where the entire load is carried. This combined with the brittle nature of the metal loops (as opposed to the flexible property of steel rope) makes chains highly vulnerable.
If you value your life and the lives of others then only lift using double-swaged co-axial steel rope!
RIP "Ray" who was slinging in NZ in 1989/90 with a chain which snapped and on the recoil entered the main rotor of a Hu500. All killed. He was a dear friend!
Thanks, that makes sense.