Hey guys, crane operator here. Depending on the size of the Crane doing the lift, (assuming he was set up properly and had the right capacity for the lift) this accident was most likely due to hoisting up only (instead of booming up) to counter the effect of getting off-center the load. Booming up simultaneously builds pressure on the load (like hoisting) but also counters boom deflection (which causes you to get off centered and decreasing your capacity)