Human operated fork lifts carry the load in front of the vehicle and operator. They have to be heavy to keep their center of gravity below and behind the load, otherwise the vehicle can tip.

These autonomous fork lifts deploy stabilizers to pick up the load, and then position it over the vehicle for transport. They don’t need to be nearly as heavy, proportionally to their load rating, as their non-autonomous counterparts.

Making it lighter, overall, just increases their power efficiency.